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:^inciples   of  nutrition  and  nutritive  ralue   of  food 


W.   0.  Atwater 


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in  2010  with  funding  from 
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http://www.archive.org/details/principlesofnutrOOatwa 


^^  Issued  March  1, 1902. 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 


FARMERS'   BULLETIN   No.  142. 


PRINCIPLES  OF  NUTRITION  AND  NUTPJTIVE 
VALUE  OF  FOOD. 

(Corrected  to  April  20, 1910;  reprinted  without  change,  January,  1916.) 


W.  O.  AXWATER,  Ph.  E>., 

Special  Agent  in  Oliarge  of  Nntrition  Investigations,  Office  of  Experiment  Stations, 


PREPARKD  UNDER  THE  SUPERVISION  OF  THE  OFFICE  OF  EXPERIMENT  STATIONS 

A.  C.  TRUE,  Director. 


WAHIIINGTON 

GOVERNMENT  PUINTINU  OFFICE 

1916 


LEHER  OF  TRANSMITTAL. 


U.  S.  Department  of  Agriculture, 

Office  of  Experiment  Stations, 
^  Washington,  D.  C,  April  5,  1906. 

Sir:  I  have  the  honor  to  transmit  herewith  an  article  on  Principles 
of  Nutrition  anu  Nutritive  Value  of  Food,  by  Prof.  W.  O.  Atwater, 
special  agent  in  charge  of  nutrition  investigations,  prepared  in  accord- 
ance with  instructions  given  by  the  Director  of  this  Office.  For  a 
number  of  years  the  Department  has  carried  on  studies  regarding  the 
kinds  and  amounts  of  foods  consumed  by  persons  of  different  occupa- 
tions and  with  different  incomes,  the  composition  of  food,  the  relative 
cost  of  nutrients  when  furnished  by  different  foods,  and  many  more 
technical  questions.  The  present  bulletin  discusses  the  general  prin- 
ciples of  nutrition,  as  well  as  a  number  of  the  more  important  phases  of 
the  subject,  with  special  reference  to  the  results  obtained  in  Depart- 
ment investigations  and  the  closely  related  work  of  the  agricultural 
experiment  stations.  As  the  work  has  progressed  the  earlier  ideas 
have  been  modified,  and  the  present  bulletin  is  designed  to  supplement 
and  replace  earher  Department  publications  by  the  author  having  a 
similar  scope.  In  preparing  this  bulletin  Professor  Atwater  has  had 
the  assistance  of  Miss  Helen  W.  Atwater. 

The  first  edition  of  this  bulletin  was  pubhshed  several  years  ago. 
In  preparing  this  edition  for  pubHcation  a  number  of  changes  which 
seemed  desirable  have  been  made. 

It  is  beheved  that  the  article  is  a  useful  summary  of  available  infor- 
mation on  the  subject,  and  its  publication  as  a  Farmers'  Bulletin  is 
therefore  recommended. 

Respectfully,  A.  C.  True, 

Director. 

Hon.  James  Wilson, 

Secretary  of  Agriculture. 

142 

(2) 


CONTENTS. 


Page. 

Introduction 5 

Chemical  composition  of  the  body  and  of  food 5 

Water 6 

Mineral  matter  or  ash 6 

Protein : 6 

Fats ; 7 

Carbohydrates 7 

Refuse 8 

Food  as  building  material  and  fuel 8 

The  body  as  a  machine 8 

Protein  as  building  material 9 

Protein  as  fuel  for  the  body 10 

Fats  and  carbohydrates  as  fuel 10 

Value  of  food  for  supplying  enei^ 10 

Heat  of  combustion 11 

The  conservation  of  energy  in  the  body 11 

Fuel  value 12 

How  the  functions  and  nutritive  value  of  food  are  learned 13 

Food  and  food  economy 14 

Composition  of  common  food  materials 15 

Proportions  of  nonnutrients  in  foods 18 

Proportions  of  nutrients  in  foods 19 

Digestion,  assimilation,  and  excretion 20 

Digestion 21 

Absorption  and  assimilation 21 

Excretion 22 

Apparent  and  actual  digestibility 22 

Ease  and  quickness  of  digestion 23 

Agreement  of  food  with  individuals 25 

Proportions  of  digestible  nutrients  in  food  materials 25 

Preparation  of  food — cooking 30 

Dietaries  and  dietary  standards 32 

Methods  of  making  dietary  studies 32 

American  and  European  dietaries  and  dietary  standards 34 

Making  home  studies  of  dietaries 37 

Adapting  fo<id  to  the  needs  of  the  body 37 

Adrantag&s  of  several  meals  a  day 38 

Pefjuniary  economy  of  food 39 

Errors  in  food  economy 43 

Needless  use  of  expensive  foods 44 

Danger  of  a  ono-sidod  diet 45 

Wa.Hto  of  food 45 

I'irrors  in  cooking 46 

Summary 47 

142 

(3) 


ILLUSTRATIONS, 


Chart  1.  Composition  of  food  materials. 
2.  Pecuniary  economy  of  food 


(4) 


PRINCIPLES  OF  NUTRITION  AND  NUTRITIVE 
VALUE  OF  FOOD. 


INTRODUCTION. 

The  problem  of  proper  nutrition  has  always  been  of  great  impor- 
tance, yet  scientific  study  of  this  subject  is  comparatively  recent.  Food 
investigations  have  been  carried  on  in  Eiu-ope  for  some  three-quarters 
of  a  century,  and  for  a  less  time  in  the  United  States.  In  recent  years 
the  development  of  this  subject  has  been  very  rapid;  a  large  number  of 
investigations  have  been  carried  on  under  the  auspices  of  this  Depart- 
ment, the  agricultural  experiment  stations,  and  various  educational 
institutions,  and  many  facts  of  interest  and  importance  have  been 
learned.  It  seems  desirable,  therefore,  to  summarize  this  informa- 
tion, and,  so  far  as  possible,  to  interpret  the  results  in  such  a  way  as 
to  show  their  practical  application. 

Constant  use  has  made  us  so  familiar  with  our  ordinary  foods  that 
we  seldom  realize  how  complicated  they  are;  yet  a  thorough  under- 
standing of  them  takes  us  far,  not  only  into  chemistry,  but  into  physics 
and  physiology  as  well. 

CHEMICAL  COMPOSITION  OF  THE  BODY  AND  OF  FOOD. 

The  chenucal  substances  of  which  the  body  is  composed  are  very 
similar  to  those  of  the  foods  which  nourish  it.  They  are  made  up  of 
the  same  chemical  elements,  and  hence  the  two  may  be  discussed 
together.  From  fifteen  to  twenty  elements  are  found,  among  the 
most  abundant  of  which  arc  oxj'^gen,  hydrogen,  carbon,  nitrogen,  cal- 
cium, phosphorus,  and  sulphur.  The  elements  are  so  combined  as  to 
form  a  great  variety  of  compounds  in  both  body  and  food.  The  most 
important  kinds  of  compounds  in  the  body  and  in  foods  are  protein, 
fats,  curbohydratcs,  mineral  matter,  and  water.  The  functions  of 
these  compounds  in  the  food,  as  explained  in  detail  later  in  this  bul- 
letin, are  to  build  and  repair  the  various  tissues  of  the  body  and  to 
8uj)ply  it  with  heat  and  muscular  energy. 

(6> 


WATER. 

Water  is  one  of  the  most  abundant  of  these  compounds.  It  forms 
over  60  per  cent  of  the  weight  of  the  body  of  the  average  man,  being  a 
component  part  of  all  the  tissues.  It  is  thus  an  important  constituent 
of  our  food,  though  it  can  not  be  burned,  and  hence  does  not  yield 
energy  to  the  body. 

MINERAL  MATTER  OR  ASH. 

Other  food  ingredients  which  yield  little  or  no  energy  and  are  yet 
indispensable  to  the  body  are  the  mineral  matters.  They  form  only  5 
or  6  per  cent  of  the  body  by  weight,  and  are  found  chiefly  in  the  bones 
and  teeth,  but  are  present  also  in  the  other  tissues  and  in  solution  in 
the  various  fluids.  When  food  or  body  material  is  burned  the  mineral 
constituents  remain  as  ash.  Phosphate  of  lime,  or  calcium  phosphate, 
is  the  mineral  basis  of  bone.  Numerous  compounds  of  potassium, 
sodium,  magnesium,  and  iron  are  found  in  the  body  and  are  necessary 
to  life. 

The  remaining  nutritive  materials  are  organic  compounds,  so  called 
because  they  occur  principally  in  the  organic,  i.  e.,  the  animal  and 
vegetable  world.  They  all  contain  carbon,  oxygen,  and  hydrogen,  in 
varying  proportions.  Some  also  contain  nitrogen,  phosphorus,  sul- 
phur, or  other  elements.  Those  occurring  in  the  body  and  in  food  are 
divided  into  three  principal  groups — protein,  fats,  and  carbohydrates. 

PROTEIN. 

This  term  includes  the  principal  nitrogenous  compounds.  Protein' 
is  familiar  to  us  in  the  lean  and  gristle  of  meat,  the  white  of  eggs,  the 
gluten  of  wheat,  etc.  It  forms  about  18  per  cent,  by  weight,  of  the 
body  of  the  average  man.  Protein  compounds  may  be  subdivided  into 
albuminoids,  gelatinoids,  and  extractives.  The  first  group,  the  albu- 
minoids, include  substances  similar  to  the  white  of  egg,  the  lean  ot 
meat  (myosin),  the  curd  of  milk  (casein),  and  the  gluten  of  wheat. 
The  second  group,  the  gelatinoids,  '^  occur  principally  in  the  connective 
tissues,  such  as  the  collagen  of  the  tendons  and  skin  and  the  ossein  of 
bone. 

The  albuminoids  and  gelatinoids,  classed  together  as  proteids,  are 
most  important  constituents  of  our  food.  They  make  the  basis  of  bone, 
muscle,  and  other  tissues,  and  are  essential  to  the  body  structure. 
They  are  also  used  as  fuel — that  is,  they  are  burned  in  the  body  to 
yield  energy — and  they  are  to  some  extent  transformed  into  fat  and 
stored  in  the  body,  but  these  are  their  less  important  uses.     The  pro- 


oThe  term  albuminoids  is  often  applied  to  what  are  here  called  gelatinoids;  the  term 
proteid  is  used  in  the  same  significance;  indeed,  there  is  great  confusion  in  the  use  of  these 
terms  by  different  writers.     The  terminology  here  followed  is  that  recommended  by  the 
American  Association  of  Agricultural  Colleges  and  Experiment  Stations. 
142 


tein  compounds  are  most  abundant  in  some  of  the  animal  foods,  as 
lean  meat,  though  the  cereals  contain  them  in  considerable,  and  peas 
and  beans  in  large,  proportions.  The  gelatinoids  are  less  valuable 
than  the  albuminoids  for  nutriment. 

The  third  class,  the  so-called  extractives,  are  included  with  the  pro- 
tein compounds  because  they  contain  nitrogen,  but  they  differ  greatly 
from  the  albuminoids  and  gelatinoids.  They  are  the  principal  ingre- 
dients of  meat  extracts,  beef  tea,  etc.  They  are  believed  to  neither 
build  tissue  nor  furnish  energy,  but  to  act  as  stimulants  and  appetizers. 
The  craving  wliich  some  persons  have  for  meat  is  perhaps  due  in  part 
to  a  desire  for  these  extractives.  The  nitrogenous  compounds  of 
potatoes  and  other  vegetable  foods  contain  more  or  less  of  so-called 
amids,  like  asparagin,  which  are  analogous  to  the  extractives  of  meat, 
and  like  them  can  not  build  tissue,  and  hence  have  an  inferior  nutri- 
tive value. 

FATS. 

Fats  occur  chiefly  in  animal  foods,  as  meats,  fish,  butter,  etc.  They 
are  also  abundant  in  some  vegetable  products,  such  as  olives  and  cot- 
ton seed,  from  which  they  are  expressed  as  oil,  and  occur  in  consider- 
able quantities  in  some  cereals,  notably  oatmeal  and  maize  (whole 
kernel),  and  in  various  nuts.  In  oiu-  bodies  and  those  of  animals  fats 
occur  in  masses  under  the  skin  and  in  other  localities,  and  in  minute 
particles  scattered  through  the  various  tissues.  The  amount  of  fat  in 
the  body  varies  greatly  with  food,  exercise,  age,  and  other  conditions. 
When  more  food  is  taken  than  is  necessary  for  immediate  use  part  of 
the  surplus  may  be  stored  in  the  body.  The  protein  and  fat  of  food 
may  thus  become  body  protein  and  body  fat;  sugar  and  starch  of 
food  are  changed  to  fat  in  the  body  and  stored  as  such.  When  the 
food  supply  is  short  this  reserve  material  is  drawn  upon  for  supple- 
mentary fuel.  Fat  forms  about  15  per  cent,  by  weight,  of  the  body 
of  an  average  man.  Well-fed  or  overfed  people  with  little  muscular 
exercise  often  grow  fat,  but  the  tendency  to  fatness  or  leanness  is 
more  or  less  a  question  of  personal  idiosyncrasy  or  some  other  little 
understood  factor,  and  not  decided  by  food  and  exercise  alone. 

CARBOHYDBATES. 

These  include  such  compounds  as  starches,  different  kinds  of  sugar, 
and  the  fiber  of  plants  or  cellulose.  They  are  found  cliiefly  in  the 
vegetable  foods,  like  cereal  grains  and  potatoes;  milk,  however,  con- 
tains considerable  amounts  of  milk  sugar,  which  is  a  carbohydrate. 
The  carbohydrates  form  only  a  very  small  proportion  of  the  body 
tissues — less  than  1  per  cent.  Starches  and  sugars,  which  are  very 
abundant  in  ortlinary  food  materials,  are  important  food  ingredients, 
bcrause  they  form  an  abundant  source  of  energy  and  are  easily 
digested.    They  may  be  and  often  are  transformed  into  fat  in  the  body. 

142 


REFUSE. 

Food,  as  we  buy  it  at  the  market  or  even  as  it  is  served  on  the  table, 
contains  more  or  less  of  materials  which  we  can  not  or  do  not  eat, 
and  which  would  have  little  or  no  nutritive  value  if  we  did  eat  them; 
such,  for  instance,  as  the  bones  of  meat  and  fish,  the  shells  of  eggs,  and 
the  skins  and  seeds  of  fruits  and  vegetables.  In  discussing  the  chem- 
ical composition  of  foods  such  portions  are  usually  counted  as  refuse, 
but  they  make  an  important  item  when  we  consider  the  actual  cost 
of  the  nutrients  of  food.  The  materials  grouped  together  as  refuse 
contain,  in  part,  the  same  ingredients  as  the  edible  portion,  though 
usually  in  very  different  proportions.  Thus  bones  are  largely  mineral 
matter,  with  some  fat  and  protein ;  eggshells  are  almost  entirely  min- 
eral matter;  bran  of  wheat  has  a  high  content  of  fiber  or  woody  mate- 
rial. Generally  speaking,  vegetable  refuse  is  characterized  by  a  high 
content  of  these  latter  constituents.  In  some  cases  material  which 
is  edible  is  classed  as  refuse  because  the  flavor  is  objectionable.  Thus 
peach  and  plum  pits  are  too  highly  flavored  to  be  agreeable  if  eaten 
in  quantitjT^,  and  are  commonly  thought  to  be  actually  injurious. 

FOOD  AS  BUILDING  MATERIAL  AND  FUEL. 
THE  BODY  AS  A  MACHINE. 

Blood  and  muscle,  bone  and  tendon,  brain  and  nerve — all  the  organs 
and  tissues  of  the  body — are  built  from  the  nutritive  ingredients  of 
food.  With  every  motion  of  the  body  and  with  the  exercise  of  feel- 
ing and  thought  as  well,  material  is  consumed  and  must  be  resupplied 
by  food.  In  a  sense,  the  body  is  a  superior  machine.  Like  other 
machines,  it  requires  material  to  build  up  its  several  parts,  to  repair 
them  as  they  are  worn  out,  and  to  serve  as  fuel.  In  some  ways  it  uses 
this  material  like  a  machine;  in  others  it  does  not.  The  steam  engine 
gets  its  power  from  fuel;  the  body  does  the  same.  In  the  one  case 
coal  or  wood,  in  the  other  food,  is  the  fuel.  In  both  cases  the  energy 
which  is  latent  in  the  fuel — the  potential  energy,  as  it  is  called  in  sci- 
entific language — is  transformed  into  power  and  heat. 

From  the  time  foods  are  taken  into  the  body  until  they  are  digested, 
absorbed,  utilized,  and  finally  converted  largely  into  the  carbon  dioxid 
and  water  vapor  of  the  breath  and  the  nitrogenous  and  other  excretory 
products  of  the  urine  and  feces,  they  undergo  great  chemical  changes, 
very  many  of  which  liberate  heat  as  a  result  of  oxidation  or  some 
closely  related  process.  It  is  through  these  complex  chemical  proc- 
esses that  the  body  derives  the  energy  for  internal  and  external  muscu- 
lar work.  Heat  is  evolved  by  such  chemical  changes  and  also  results 
from  the  muscular  work  of  the  body,  and  there  is  reason  to  believe  that 
within  wide  limits  the  heat  thus  produced  is  sufficient  for  maintain- 
ing body  temperature.     The  amount  of  heat  produced  in  the  body 


9 

must,  or  course,  vary  with  the  amount  of  food  eaten,  the  work  done, 
and  other  circumstances.  However,  the  body  is  such  a  perfect  piece 
of  mechanism  that  the  loss  of  heat  by  radiation,  etc.,  is  so  adjusted 
to  heat  production  that  body  temperature  remains  fairly  constant. 

One  important  dijQPerence  between  the  human  machine  and  the 
steam  engine  is  that  the  former  is  self-building,  self-repairing,  and 
self-regulating.  Another  is  that  the  material  of  which  the  engine  is 
built  is  verj  different  from  that  which  it  uses  for  fuel,  but  part  of  the 
material  which  serves  the  body  as  a  source  of  energy  also  builds  it  up 
and  keeps  it  in  repair.  Furthermore,  the  body  can  use  its  o^vn  sub- 
stance for  this  purpose.  This  the  steam  engine  can  not  do.  The 
steam  engine  and  the  body  are  alike  in  that  both  convert  the  fuel  into 
mechanical  power  and  heat.  They  differ  in  that  the  body  uses  the 
same  material  for  fuel  as  for  building  and  also  consumes  its  own  mate- 
rial for  fuel.  In  the  use  of  its  source  of  power  the  body  is  much  more 
economical  than  any  engine. 

But  the  body  is  more  than  a  machine.  It  has  not  simply  organs  to 
build  and  keep  in  repair  and  supply  with  energy;  it  has  a  nervous 
organization;  it  has  sensibilities;  and  there  are  the  higher  intellectual 
and  spiritual  faculties.  The  right  exercise  of  these  depends  upon  the 
right  nutrition  of  the  body. 

The  chief  uses  of  food,  then,  are  two:  (1)  To  form  the  material  of 
the  body  and  repair  its  wastes,  and  (2)  to  furnish  muscular  and  other 
power  for  the  work  the  body  has  to  do  and  yield  heat  to  keep  the  body 
warm.  In  forming  the  tissues  and  the  fluids  of  the  body  the  food 
serves  for  building  and  repair.  In  yielding  power  and  heat  it  serves 
as  fuel. 

If  more  food  is  eaten  than  is  needed,  more  or  less  of  the  surplus  may 
be  and  sometimes  is  stored  in  the  body,  chiefly  in  the  form  of  fat.  The 
fat  in  the  body  forms  a  sort  of  reserve  supply  of  fuel  and  is  utilized  in 
the  place  of  food.  When  the  work  is  hard  or  the  food  supply  is  low 
the  body  draws  upon  this  store  of  fat  and  grows  lean. 

PROTEIN  AS  BUILDING  MATERIAL. 

The  principal  tissue  formers  are  the  protein  compounds,  especially 
the  albuminoids.  These  make  the  framework  of  the  body.  They 
build  up  and  repair  the  nitrogeneous  materials,  as  the  muscles  and  ten- 
dons, and  supply  the  albuminoids  of  the  blood,  milk,  and  other  fluids. 

The  albuminoids  of  food  arc  transformed  into  the  albuminoids  and 
gelatinoids  of  the  body.  Muscle,  tendon  and  cartilage,  bone  and  skin, 
the  corpuscles  of  the  blood,  and  the  casein  of  milk  are  made  of  the 
albuminoids  of  food.  The  albuminoids  are  sometimes  called  "flesh 
formers"  or  "muscle  formers,"  because  the  lean  flesh,  the  muscle,  is 
made  from  them,  though  the  term  is  inadequate,  as  it  leaves  out  of 
account  the  energy-furnishing  function  of  protein.  The  gelatinoids  of 
food,  8uch  as  the  finer  particles  of  tendon  and  the  gelatin,  which  are 

20565"— Bull.  142—16 2 


10 

dissolved  out  of  bone  and  meat  in  soup,  though  somewhat  similar  to 
the  albuminoids  in  composition,  are  not  believed  to  be  tissue  formers; 
but  they  are  valuable  in  protecting  the  albuminoids  from  consumption. 
That  is,  when  the  food  contains  gelatinoids  in  abundance  less  of  albu- 
minoids is  used. 

The  proteids  can  be  so  changed  in  the  body  as  to  yield  fats  and  car- 
bohydrates, and  such  changes  actually  occur  to  some  extent.  In  this 
and  other  ways  they  supply  the  body  with  fuel. 

PROTEIN  AS  FUEL.  FOR  THE  BODY. 

The  protein  compounds  are  not  only  used  for  building  and  repairing 
tissue,  but  are  also  burned  directly  in  the  body  like  the  carbohydrates, 
and  thus  render  important  service  as  fuel.  A  dog  can  live  on  lean 
meat.  He  can  convert  its  material  into  muscle  and  its  energy  into 
heat  and  muscular  power.  Man  can  do  the  same;  but  such  a  one- 
sided diet  would  not  be  best  for  the  dog  and  it  would  be  still  worse  for 
man.  The  natural  food  for  carniverous  animals,  hke  the  dog,  supplies 
fats  and  some  carbohydrates,  and  that  for  omnivorous  animals,  like 
man,  furnishes  fats  and  carbohydrates  in  liberal  amounts  along  with 
protein.  Herbivorous  animals,  like  horses,  cattle,  and  sheep,  naturally 
require  large  proportions  of  carbohydrates. 

FATS  AND  CARBOHYDRATES  AS  FUEL. 

Fats  and  carbohydrates  are  the  chief  fuel  ingredients  of  food.  Sugar 
and  the  starch  of  bread  and  potatoes  are  burned  in  the  body  to  yield 
heat  and  power.  The  fats,  such  as  the  fat  of  meat  and  butter,  serve 
the  same  purpose,  only  they  are  a  more  concentrated  fuel  than  the 
carbohydrates. 

The  body  can  also  transform  carbohydrates  of  food  into  fat.  This 
fat,  and  with  it  that  stored  from  the  food,  is  kept  in  the  body  as  reserve 
fuel  in  the  most  concentrated  form. 

The  different  nutrients  can  to  a  greater  or  less  extent  do  one  another's 
work.  If  the  body  has  not  enough  of  one  kind  of  fuel  it  can  use 
another.  But,  while  protein  can  be  burned  in  the  place  of  fats  and 
carbohydrates,  neither  of  the  latter  can  take  the  place  of  the  albumi- 
noids in  building  and  repairing  the  tissues.  •  At  the  same  time  the  gela- 
tinoids, fats,  and  carbohydrates,  by  being  consumed  themselves,  pro- 
tect the  albuminoids  from  consumption. 

VALUE  OF  FOOD  FOR  SUPPLYING  ENERGY. 

Heat  and  muscular  power  are  forms  of  force  or  energy.  The  energy 
latent  in  the  food  is  developed  as  the  food  is  consumed  in  the  body. 
The  process  is  more  or  less  akin  to  that  which  takes  place  when  coal  is 
burned  in  the  furnace  of  the  locomotive.  For  the  burning  of  the  food 
in  the  body  or  the  coal  in  the  furnace,  air  is  used  to  supply  oxygen. 

142 


11 

When  the  fuel  is  oxidized,  be  it  meat  or  wood,  bread  or  coal,  the  latent 
energy  becomes  active,  or,  in  technical  language,  the  potential  energy 
becomes  kinetic;  it  is  transformed  into  power  and  heat.  As  various 
kinds  of  coal  differ  in  the  amoiuit  of  heat  given  off  per  ton,  so  various 
kinds  of  food  and  food  ingredients  give  off  different  amounts  of  energy; 
that  is,  have  different  values  as  fuel  in  the  body. 

HEAT  OF  COMBUSTION. 

The  processes  of  oxidation  of  material  and  transformation  of  energy 
in  the  body  are  less  simple  than  in  the  engine  and  less  clearly  under- 
stood. Late  research,  however,  has  given  us  ways  of  measuring  the 
energy  latent  in  coal,  wood,  and  in  food  materials  as  well.  This  is 
most  generally  done  in  the  chemical  laboratory  by  an  apparatus  called 
the  bomb  calorimeter.  The  amount  of  heat  given  off  in  the  oxidation 
01  a  given  quantity  of  any  material  is  called  its  "heat  of  combustion," 
and  is  taken  as  a  measure  of  its  latent  or  potential  energy.  The  unit 
commonly  used  is  the  calorie,  the  amount  of  heat  which  would  raise 
the  temperature  of  1  kilogram  of  water  1°  C,  or,  what  is  nearly  the 
same  thing,  1  pound  of  water  4°  F.  Instead  of  this  unit  of  heat  a  unit 
of  mechanical  energy  may  be  used — for  instance,  the  foot-ton,  which 
represents  the  force  required  to  raise  1  ton  1  foot.  One  calorie  is  equal 
to  very  nearly  1.54  foot-tons;  that  is  to  say,  1  calorie  of  heat,  when 
transformed  into  mechanical  power,  would  suffice  to  lift  1  ton  1.54  feet. 

THE  CONSERVATION  OF  ENERGY  IN  THE  BODY. 

The  amounts  of  energy  transformed  in  the  body  when  food  and  its 
own  material  are  burned  within  it  are  measured  with  the  respiration 
calorimeter  referred  to  on  page  13.  It  is  well  known  that  the  food  is  not 
completely  oxidized  in  the  body.  These  experiments  have  shown  that 
the  material  which  is  oxidized  yields  the  same  amount  of  energy  as  it 
would  if  burned  with  oxygen  outside  the  body,  e.  g.,  in  the  bomb 
calorimeter.  The  experiments  show  also  that  when  a  man  does  no 
muscular  work  (save,  of  course,  the  internal  work  of  respiration,  circu- 
lation, etc.),  all  the  energy  leaves  his  body  as  heat;  but  when  he  does 
muscular  work,  as  in  Ufting  weights  or  driving  a  bicycle,  part  of  the 
energy  appears  in  the  external  work  thus  done,  and  the  rest  is  given 
off  from  the  body  as  heat.  The  most  interesting  result  of  all  is  that 
the  energy  given  off  from  the  body  as  heat  when  the  man  is  at  rest, 
or  as  heat  and  mechanical  work  together  when  he  is  working,  exactly 
equals  the  latent  energy  of  the  material  burned  in  the  body.  This  is 
in  accordance  with  the  law  of  the  conservation  of  energy.  It  thus 
appears  that  the  body  actually  obeys,  as  we  should  expect  it  to  obey, 
this  great  law  which  dominates  the  physical  universe. 

143 


12 

FTJEL.  VALUE. 

We  may  make  practical  application  of  this  principle  of  the  conser- 
vation of  energy  in  the  body  in  measuring  the  actual  value  of  food  as 
fuel  to  the  body,  i.  e.,  its  "  fuel  value,"  by  use  of  the  bomb  and  respira- 
tion calorimeters.  To  do  this  we  have  to  take  into  account  the  chem- 
ical composition  of  the  food,  the  proportions  of  the  nutrients  actually 
digested  and  oxidized  in  the  body,  and  the  proportion  of  the  whole 
latent  energy  of  each  which  becomes  active  and  useful  to  the  body  for 
warmth  and  work.  Taldng  our  common  food  materials  as  they  are 
used  in  ordinary  diet,  the  following  general  estimate  has  been  made 
for  the  energy  furnished  to  the  body  by  1  gram  or  1  pound  of  each  of 
the  classes  of  nutrients:'* 

Protein,  fuel  value,  4  calories  per  gram,  or  1,820  calories  per  pound. 
Fats,  fuel  value,  9  calories  per  gram,  or  4,040  calories  per  pound. 
Carbohydrates,  fuel  value,  4  calories  per  gram,  or  1,820  calories  per  pound. 

It  will  be  seen  that  when  we  compare  the  nutrients  in  respect  to  their 
fuel  value,  their  capacities  for  yielding  heat  and  mechanical  power,  a 
pound  of  protein  of  lean  meat  or  albumen  of  egg  is  just  about  equiva- 
lent to  a  pound  of  sugar  or  starch,  and  a  little  over  2  pounds  of  either 
would  be  required  to  equal  a  pound  of  the  fat  of  meat  or  butter  or  of 
body  fat. 

The  fuel  value  of  food  obviously  depends  upon  the  amounts  of  actual 
nutrients,  and  especially  upon  the  amount  of  fat  it  contains.  Thus  a 
pound  of  wheat  flour,  which  consists  largely  of  starch,  has  an  average 
fuel  value  of  about  1,625  calories,  and  a  pound  of  butter,  which  is 
mostly  fat,  about  3,410  calories.  These  are  only  about  one-eighth 
water.  Whole  milk,  which  is  seven-eighths  water,  has  an  average 
fuel  value  of  310  calories  per  pound;  cream,  which  has  more  fat  and 
less  water,  865  calories,  and  skim  milk,  which  is  whole  milk  af"ter  the 
cream  has  been  removed,  165  calories. 

This  high  fuel  value  of  fat  explains  the  economy  of  nature  in  storing 
fat  in  the  body  for  use  in  case  of  need.  Fat  is  the  most  concentrated 
form  of  body  fuel. 

We  have  been  considering  food  as  a  source  of  heat  and  muscular 
power.  There  is  no  doubt  that  intellectual  activity,  also,  is  somehow 
dependent  upon  the  consumption  of  material  which  the  brain  has 
obtained  from  the  food;  but  just  what  substances  are  consumed  to 
produce  brain  and  nerve  force,  and  how  much  of  each  is  required  for 
a  given  quantity  of  intellectual  labor,  are  questions  which  the  physio- 
logical chemist  has  not  yet  answered. 

o  These  estimates  are  based  upon  the  latest  and  most  reliable  research  and  take  into 
account  only  the  material  which  is  digested  and  oxidized  so  that  its  energy  is  actually 
available  to  the  body.  EarHer  estimates,  based  on  less  accurate  data  and  not  making 
allowance  for  the  amounts  of  fats  and  carbohydrates  which  escape  oxidation  in  the  body, 
give  4.1  calories  per  gram,  or  1,860  calories  per  pound,  for  protein  and  carbohydrates  and 
9.3  calories  per  gram,  or  4,220  for  fats,  figures  which  have  come  into  common  use. 


I 


13 

HOW   THE    FUNCTIONS  AND   NUTEITIVE   VALUE    OF    FOOD   ARE 

LEARNED. 

The  principles  above  explained  are  based  upon  a  great  deal  of 
experimenting  and  observation.  The  experimenting  is  of  many 
kinds,  but  of  especial  importance  is  the  work  with  the  respiration 
apparatus  and  respiration  calorimeter. 

Various  forms  of  respiration  apparatus  have  been  devised  within 
the  last  fifty  years.  Among  the  most  important  are  those  invented 
bv  Pettenkofer  and  Voit  in  Munich.  They  consist  of  metal-walled 
chambers  large  enough  for  the  subject  (sometimes  a  man,  sometimes 
a  dog,  sheep,  or  other  animal)  to  live  in  comfortably  for  several  days, 
and  are  furnished  with  devices  for  pumping  air  through  and  measur- 
ing and  analyzing  it  as  it  enters  and  leaves  the  chamber.  With 
such  an  apparatus  it  is  possible  not  only  to  measure  all  the  food  and 
excreta,  but  also  the  materials  given  off  from  the  lungs  in  the  breath, 
and  to  make  accurate  determinations  of  the  matter  entering  and  leav- 
ing the  body. 

A  still  more  elaborate  apparatus,  by  which  not  only  all  the  matter 
passing  in  and  out  of  the  body  may  be  measured,  but  also  all  the  heat 
given  off  from  it,  is  called  a  respiration  calorimeter — that  is,  a  machine 
for  measuring  both  the  respiratory  products  and  the  heat  given  off  by 
the  body.  It  is  like  the  respiration  apparatus,  except  that  it  is  fur- 
nished with  devices  for  measuring  temperatures.  Several  have  been 
built  in  Europe  within  the  last  twenty  years,  among  the  most  success- 
ful being  those  by  Rubncr  and  Rosenthal.  °'  Investigations  in  coop- 
eration with  the  United  States  Department  of  Agriculture  are  now 
being  carried  on  in  one  recently  built  by  the  author  and  Professor 
Rosa  at  Wesleyan  University.''  Its  main  feature  is  a  copper-walled 
chamber  7  feet  long,  4  feet  wide,  and  6  feet  4  inches  high.  This  is 
fitted  with  devices  for  maintaining  and  measuring  a  ventilating  cur- 
rent of  air,  for  sampling  and  analyzing  this  air,  for  removing  and 
measuring  the  heat  given  off  within  the  chamber,  and  for  passing  food 
and  other  articles  in  and  out.  It  is  furnished  with  a  folding  bed, 
chair,  and  table,  with  scales  and  with  appliances  for  muscular  work, 
and  has  telephone  connection  with  the  outside.  Here  the  subject 
stays  for  a  period  of  from  three  to  twelve  days,  during  which  time  care- 
ful analyses  and  measurements  are  made  of  all  material  which  enters 
the  body  in  the  food  and  of  that  which  leaves  it  in  the  breath  and 
excreta.  Record  is  also  kept  of  the  energy  given  off  from  the  body  as 
heat  and  muscular  work.  The  differences  between  the  material  taken 
into  and  that  given  <jff  from  the  body  is  called  the  balance  of  matter, 
and  shows  whether  the  body  is  gaining  or  losing  material.     The  dif- 

«U.  S.  Dnpt.  Agr.,  Offic«  of  Experiment  Stations  Bui.  21,  p.  1.33. 
^V .  S.  Dept.  Apr.,  Office  of  Experiment  Stations  Bui.  63. 


14 

ference  between  the  energy  of  the  food  taken  and  that  of  the  excreta 
and  the  energy  given  off  from  the  body  as  heat  and  muscular  work,  is 
the  balance  of  energy,  and  if  correctly  estimated  should  equal  the 
energy  of  the  body  material  gained  or  lost. 

With  such  apparatus  it  is  possible  to  learn  what  effect  different 
conditions  of  nourishment  will  have  on  the  human  body.  In  one 
experiment,  for  instance,  the  subject  might  be  kept  quite  at  rest,  and 
in  the  next  do  a  certain  amount  of  muscular  or  mental  work,  with  the 
same  diet  as  before.  Then  by  comparing  the  results  of  the  two  the 
use  which  the  body  makes  of  its  food  under  the  different  conditions 
could  be  determined.  Or  the  diet  may  be  slightly  changed  in  one 
experiment  and  the  effect  of  this  on  the  balance  of  matter  and  energy 
observed.  Such  methods  and  apparatus  are  very  costly  in  time  and 
money,  but  the  results  are  proportionately  more  valuable  than  those 
from  simpler  experiments. 


FOOD  AND  FOOD  ECONOMY. 

What  has  thus  far  been  said  about  the  ingredients  of  food  and  the 
ways  they  are  used  in  the  body  may  be  briefly  summarized  in  the 
following  schematic  manner: 

Nutritive  ingredients  {or  nutrients)  of  food. 

"Water. 


Food  as  purchased 
contains — 


Edible  portion 

e.  g.,  flesh  of  meat,  yolk  and  white 
of  eggs,  wheat,  flour,  etc. 

Refuse, 
e.  g.,  bones,  entrails,  shells,  bran,  etc. 


Nutrients...- 


Protein. 
Fats. 

Carbohydrates. 
Mineral  matters. 


All  serve  as  fuel  to  yield 
energy  in  the  forms  of 
heat  and  muscular 
power. 


Uses  of  nutrients  in  the  iody. 

Protein Forms  tissue 

e.  g.,  white  (albumen)  of  eggs, 

curd   (casein)   of  nailk,   lean 

meat,  gluten  of  wheat,  etc. 
Fats Are  stored  as  fat 

e.  g.,  fat  of  meat,  butter,  olive 

oil,  oils  of  com  and  wheat, 

etc. 
Carbohydrates Are  transformed  into  fat 

e.  g.,  sugar,  starch,  etc. 
Mineral  matters  (ash) Share  in  forming  bone,  assist  in  digestion,  etc. 

e.  g.,  phosphates  of  lime,  pot- 
ash, soda,  etc. 

The  views  thus  presented  lead  to  the  following  definitions :  (1)  Food 
is  that  which,  taken  into  the  body,  builds  tissues  or  yields  energy; 

142 


15 

(2)  the  most  healthful  food  is  that  which  is  best  fitted  to  the  needs  of 
the  user;  (3)  the  cheapest  food  is  that  which  furnishes  the  largest 
amount  of  nutriment  at  the  least  cost;  and  (4)  the  best  food  is  that 
which  is  both  most  healthful  and  cheapest. 

We  have,  then,  to  consider  the  kinds  and  amounts  of  nutrients  in 
different  food  materials,  their  digestibility,  the  kinds  and  amoimts 
needed  for  nourishment  by  persons  under  different  conditions  of  rest 
and  work,  and  the  nutritive  value  of  different  food  products  as  com- 
pared with  their  cost. 

COMPOSITION  OF  COMMON  FOOD  MATERIALS. 

The  value  of  food  for  nutriment  depends  mainly  upon  its  composi- 
tion and  digestibility.  The  composition  of  foods  is  determined  by 
chemical  analysis.  The  first  effective  impulse  to  the  systematic  study 
of  the  chemistry  of  foods  was  given  by  Liebig  somewhat  over  50  years 
ago,  but  nearly  all  of  our  definite  knowledge  of  the  chemical  composi- 
tion of  food  materials  has  accumulated  Avithin  comparatively  a  few 
years  past. 

Until  about  the  year  1880  those  who  wished  to  know  about  the 
chemical  composition  of  food  materials  were  compelled  to  depend 
upon  analyses  of  European  products,  and  most  of  those  analyses  had 
been  made  in  German  laboratories.  During  the  last  two  decades, 
however,  American  investigations  have  accumulated  until  at  the  pres- 
ent time  the  results  of  over  4,000  analyses  of  food  materials  from  dif- 
ferent parts  of  the  United  States  are  available.  A  large  proportion 
of  these  analyses  have  been  made  during  the  last  few  years  in  connec- 
tion with  nutrition  investigations  under  the  auspices  of  the  Depart- 
ment of  Agriculture. 

The  methods  of  chemical  analysis  of  foods  are  now  so  nearly  uni- 
form throughout  the  world  that  the  analyses  reported  from  different 
countries  furnish  a  reliable  means  of  comparing  the  composition  of 
the  food  products  of  different  parts  of  the  world. 

Table  I  shows  the  average  composition  of  ordinary  American  food 
materials  as  calculated  from  the  analyses  now  available. "  The  value 
of  food  as  influenced  by  digestibility  is  discussed  later.  (See  Table  II, 
p.  27.) 

oCondensed  from  U.  S.  Dept.  Agr.,  Office  of  ExperimeDt  Stations  Bui.  28,  revised. 
142 


16 


Table  I. — Average  composition  of  common  American  food  products. 


Food  materials  (as  purchased) . 

Refuse. 

Water. 

Pro- 
tein. 

Fat. 

Carbo- 
hy- 
drates. 

Ash. 

Fuel 

value 

per 

pound. 

ANIMAL  FOOD. 

Beef,  fresh : 

Per  ct. 
16.3 
10.2 
13.3 

12.7 
12.8 
27.6 
20.8 

Per  ct. 
52.6 
54.0 
52.5 
52.4 
54.0 
45.9 
43.8 
63.9 
60.7 
45.0 
42.9 
56.8 
49.1 
50.4 

49.2 
58.9 
53.7 
51.8 
51.8 

52.0 
60.1 
68.3 
54.2 
56.2 

39.0 
51.2 
42.0 
41.6 
45.4 

45.5 
52.9 

48.0 
41.8 
44.9 
66.5 

34.8 

36.8 

7.9 

17.4 

55.2 
39.8 
57.2 

88.6 
92.9 
84.5 
90.0 

43.7 
47.1 
38.5 
42.4 

58.5 
61.9 
40.4 
50.7 
35.2 
71.2 

40.2 
19.2 

63.5 
53.6 

88.3 
80.8 
36.7 
30.7 

)il. 

Per  ct. 
15.5 
17.0 
16.1 
19.1 
16.5 
14.5 
13.9 
19.3 
19.0 
13.8 
12.8 
16.4 
14.5 
15.4 

14.3 
11.9 
26.4 
25.5 
26.3 

15.4 
15.5 
20.1 
15.1 
16.2 

13.8 
15.1 
13.5 
12.3 
13.8 

15.4 
15.9 

13.5 
13.4 
12.0 
18.9 

14.2 

13.0 

1.9 

9.1 

18.2 
13.0 
19.6 

2.1 
4.4 
4.6 
1.8 

12.8 
13.7 
13.4 
16.1 

11.1 
15.3 
10.2 
12.8 
9.4 
20.9 

16.0 
20.5 

21.8 
23.7 

6.0 
10.6 
7.9 
5.9 

Per  ct. 
15.0 
19.0 
17.5 
17.9 
16.1 
11.9 
21.2 
16.7 
12.8 
20.2 
7.3 
9.8 
17.5 
18.3 

23.8 
19.2 
6.9 
22.5 
18.7 

11.0 
7.9 
7.5 
6.0 
6.6 

36.9 
14.7 
28.3 
24.5 
23.2 

19.1 
13.6 

25.9 
24.2 
29.8 
13.0 

33.4 
26.6 
86.2 
62.2 

19.7 
44.2 
18.6 

2.8 

.4 

4.3 

1.1 

1.4 
12.3 
29.8 
18.4 

.2 
4.4 
4.2 

.7 
4.8 
3.8 

.4 

8.8 

12.1 
12.1 

1.3 

1.1 

.9 

,7 

Per  ct. 

----- 

1.1 

5.0 
1.1 
5.5 
5.6 

""2.& 

3.3 

5.2 

.6 

9 

Per  ct. 
0.8 
.7 
.9 
.8 
.9 
.7 
.7 
.9 
1.0 
.7 
.6 
.9 
.7 
.7 

4.6 
4.3 
8.9 
1.3 
4.0 

.8 

.9 

1.0 

.7 
.8 

.6 
.8 

.7 

.7 

•     .7 

.8 
.9 

.8 
.8 
.7 
1.0 

4.2 
5.5 
3.9 
4.1 

3.8 
2.2 
3.4 

1.5 
1.2 
1.1 
1.5 

.7 
.7 
.7 
.8 

.8 
.9 
.7 
.9 
.7 
1.5 

18.5 

7.4 

2.6 
5.3 

1.1 
2.3 
1.5 

9. 

Calo- 
ries. 
910 

Flank. 

1,105 

1,025 

1,100 

975 

1,165 

Ribs                           

1,135 

Rib  rolls 

1,055 

7.2 
20.7 
36.9 
16.4 
18.7 
15.7 

8.4 
6.0 

4.7 

890 

Rump 

1,090 

545 

715 

995 

1,045 

Beef,  come  J,  canned,  pickled,  and  dried: 

1,245 

Tongue,  pickled  

1,010 

790 

1,410 

1,270 

Veal: 

21.3 
14.2 
3.4 
24.5 
20.7 

9.9 
18.4 
16.0 
21.2 

17.2 

19.1 
17.4 

10.7 
19.7 
12.4 

13.6 
18.2 

745 

Leg             

625 

695 

535 

Hiiid  quarter. .             .                 

580 

Mutton: 

1,770 

890 

1,415 

1,235 

Hind  quarter,  without  tallow . . 

1,210 

Lamb: 

1,075 

860 

Ham 

1,320 

1,245 

1,450 

Tenderloin 

895 

Pork,  salted,  cured,  and  pickled : 

Ham,  smoked 

1,635 

Shoulder,  smoked 

1,335 

Salt  pork : 

3,555 

7.7 
3.3 

2,715 

Sausage: 

Bologna 

1,155 

Pork 

2,075 

1,155 

Soups : 

Celery,  cream  of 

235 

Beef 

120 

365 

Tomato 

185 

Poultry : 

Chicken,  broilers . 

41.6 
25.9 
17.6 
22.7 

29.9 
17.7 
44.7 
35.1 
50.1 

305 

Fowls 

765 

Goose 

1,475 

Turkey 

1,060 

Fish: 

Cod,  dressed 

220 

HaHbut,  steaks  or  sections 

475 

370 

Perch,  yellow,  dressed 

275 

Shad,  whole 

380 

Shad,  roe 

600 

Fish,  preserved: 

24.9 
44.4 

325 

Herring,  smoked  .                 

755 

Fish,  canned: 
Salmon 

915 

Sardines 

O5.0 

950 

Shellfish: 

Oysters,  "  solids  " 

* 

225 

Clams 

340 

Crabs 

52.4 
61.7 

Refuse,  ( 

200 

Lobsters 

145 

o] 

142 


17 

Table  I. — Average  composition  of  common  American  food  products — Continued. 


Food  raaterials  (as  purchased). 


A24IMAL  FOOD — continued. 


Eggs:  Hens'  eggs 

Dairy  products, etc.; 

Butter 

Whole  milk 

Skiin  milk 

Buttennilk 

Condensed  milk. . 

Cream 

Cheese, Cheddar. . 

Cheese,  full  cream . 


Refuse 


Per  ct. 
a  11. 2 


Water.l 


Pro- 
tein. 


VEGETABLE   FOOD. 

Flour,  meal,  etc.: 

Entire-wheat  flour 

Graham  flour 

Wheat  flour,  patent  roller  process- 
High-grade  and  medium 

Low  grade 

Macaroni,  vermiceUi,etc 

Wheat  breakfast  food 

Buckwheat  flour 

Rye  flour 

Com  meal 

Oat  breakfast  food 

Rice 

Tapioca 

Starch 

Bread,  past ry . etc. : 

White  bread 

Brown  bread 

Graham  bread 

Whole-wheat  bread 

Rve  bread 

Cake 

Cream  cracker.s 

Oyster  crackers 

Soda  crackers 

Sugars,  etc.: 

Molasses 

Candy  6 

Honey 

Sugar,  granulated 

Mnple  sirup 

VegetaDles:<: 

Beans,  dried 

Beans,  Lima,  shelled 

Beans,  string 

Beets 

Cabbage 

Celery 

Com, green  (sweet), edible  portion 

Cucumbers 

Lettuce 

Mu.sh  rooms 

Onions 

Parsnips 

Peas  (Pixum  aativum), dried 

Peas  <  Pinum  sativum) ,  shelled 

Cowpeas,  dried 

Potatoes 

Rhubarb 

Sweet  potatoes 

Spinach 

Squa.*ih 

Tomatoes 

Turnips 

VegetHblfM.ciinned: 

Baked  l)Pitns 

Peas  (Piinm  »alirum).gTof'T\ 

Com.grofn 

Succotash 

Tomatoes 


10.0 
20.0 


20.0 
40.0 
20.0 


50.0 


30.0 


Per  ct. 
65.5 

11.0 
87.0 
90.5 
91.0 
26.9 
74.0 
27.4 
34.2 


11.4 
11.3 

12.0 
12.0 
10.3 

9.6 
13.6 
12.9 
12.5 

7.7 
12.3 
11.4 


35.3 

43.6 

35.7 

38.4 

35.7 

19.9 

6.8 

4.8 

5.9 


Per  ct. 
13.1 

1.0 
3.3 
3.4 
3.0 

8.8 

2.5 

27.7 

25.9 


13.8 
13.3 

11.4 
14.0 
13.4 
12.1 
6.4 
6.8 
9.2 
16.7 
8.0 
.4 


9.2 
5.4 
8.9 
9.7 
9.0 
6.3 
9.7 
11.3 
9.8 


Fat. 


12.6 
68.5 
83.0 
70.0 
77.7 
75.6 
75.4 
81.1 
80.5 
88.1 
78.9 
66.4 
9.5 
74.6 
13.0 
62.6 
56.6 
55.2 
92.3 
44.2 
94.3 
62.7 

68.  g 
85.3 
76.1 
76.9 
94.0 


2^.5 

7.1 

2.1 

1.3 

1.4 

.9 

.3.1 

.7 

1.0 

3.5 

1.4 

1.3 

24.6 

7.0 

21.4 

1.8 

.4 

1.4 

2.1 

.7 

.9 

.9 

6.9 
3.6 
2.8 
.3.0 
1.2 


Per  ct. 
9.3 

85.0 

4.0 

.3 

.5 

8.3 

18.5 

36.8 

33.7 


1.9 
2.2 

1.0 
1.9 

.9 
1.8 
1.2 

.9 
1.9 
7.3 

.3 

.1 


1.3 

1.8 

1.8 

.9 

.6 

9.0 

12.1 

10.5 

9.1 


1.8 
.7 
.3 
.1 
.2 
.1 

1.1 
.2 
2 

.4 
.3 
.4 

1.0 
.5 

1.4 
.1 
.4 
.6 
.3 
.2 
.4 
.1 

2.5 
.2 
1.2 
1.0 
.2 


Carbo- 
hy- 
drates. 


Ash. 


Per  ct.    Per  ct. 
0.9 


5.0 
5.1 
4.8 
54.1 
4.5 
4.1 
2.4 


71.9 
71.4 

75.1 
71.2 

75.2 
77.9 
78.7 
75.4 
66.2 
79.0 
88.0 
90.0 


70.0 
96.0 
81.0 
100.0 
71.4 

59.6 

22.0 

6.9 

7.7 

4.8 

2.6 

19.7 

2.6 

2.5 

6.8 

8.9 

10.8 

62.0 

16.9 

60.8 

14.7 

2.2 

21.9 

3.2 

4.5 

.19 

5.7 

19.6 
0.8 
19.0 
18.6 
4.0 


3.0 

.7 


1.9 

.5 

4.0 

3.8 


1.0 
1.8 

.5 

.9 

1.3 

1.3 

.9 

.7 

1.0 

2.1 

.4 

.1 


.5,3. 1 

1.1 

47.1 

2.1 

,'>2.1 

1.5 

49.7 

1.3 

53. 2 

1.5 

63.3 

1.5 

69.7 

1.7 

70. 5 

2.9 

73.1 

2.1 

3.5 

1.7 

.7 

.9 

.9 

.8 

.7 

.4 

.8 

1.2 

.  5 

1.1 

2.9 

1.0 

3.4 


2.1 
.4 


2.1 
1.1 
.9 
.0 
.0 


n  Uefu.se,  shell. 

6  Plain  confectionery  not  containing  nuts,  fruit,  or  chocolate. 

«8iich  vegetables  as  potatoes,  squash,  beets,  etc.,  have  ii  f;<'rtain  amount  of  inedible  material,  skin, 
iteedH,  t'U;.  The  amount  varies  with  the  method  of  pr(f)arinK  the  vegetables,  and  can  not  be  accu- 
rately estimated.  The  flgurcs  given  for  refuse  of  vcgetalil(!H,  fruits,  etc.,  are  assumed  to  represent 
approximately  the  amount  of  refuM  In  these  foods  as  ordinarily  prepared. 

20555''     Bull.  1-12-16—^3 


18 


Table  I. — Average  composition  of  common  American  food  products — Continued. 


Food  materials  (as  purchased). 


VEGETABLE  FOOD — continued. 

Fruits,  berries,  etc.,  fresh:  a 

Apples 

Bananas 

Grapes 

Lemons 

Muskmelons 

Oranges 

Pears 

Persimmons,  edible  portion 

Raspberries 

Strawberries ^ 

Watermelons 

Fruits,  dried: 

Apples 

Apricots 

Dates 

Figs 

Raisins 

Nuts: 

Almonds 

Brazil  nuts 

Butternuts 

Chestnuts,  fresh 

Chestnuts,  dried 

Cocoanuts 

Cocoanut,  prepared 

Filberts 

Hickory  nuts 

Pecans,  polished 

Peanuts 

Pinon  (Pinus  edulis) 

Walnuts,  black 

Walnuts,  English 

Miscellaneous: 

Chocolate 

Cocoa,  powdered 

Cereal  coffee,  infusion  (1  part  boiled  in 
20  parts  water)  c 


Refuse. 


Per  ct. 
25.0 
35.0 
25.0 
30.0 
60.0 
27.0 
10.0 


5.0 
59.4 


10.0 

"io.'o 


Per  ct. 
63.3 
48.9 
58.0 
62.5 
44.8 
63.4 
76.0 
66.1 
85.8 
85.9 
37.5 

28.1 
29.4 
13.8 
18.8 
13.1 

2.7 

2.6 

.6 

37.8 

4.5 

7.2 

3.5 

1.8 

1.4 

1.4 

6.9 

2.0 

.6 

1.0 

5.9 
4.6 


Pro- 
tein. 


Per  ct. 

0.3 
.8 

1.0 
.7 
.3 
.6 
.5 
.8 

1.0 
.9 
.2 

1.6 
4.7 
1.9 
4.3 
2.3 

11.5 
8.6 
3.8 
5.2 
8.1 
2.9 
6.3 
7.5 
6.8 
5.2 

19.5 
8.7 
7.2 
6.9 

12.9 
21.6 


Fat. 


Per  ct. 
0.3 

.4 
1.2 

.5 


.6 
.1 

2.2 
1.0 
2.5 
.3 
3.0 

30.2 
33.7 
8.3 
4.5 
5.3 
25.9 
67.4 
31.3 
25.5 
33.3 
29.1 
36.8 
14.6 
26.6 

48.7 
28.9 


Carbo- 
hy- 
drates. 


Ash. 


Per  ct. 

10.8 

14.3 

14.4 

6.9 

4.6 

8.5 

12.7 

31.5 

12.6 

7.0 

2.7 

66.1 
62.6 
70.6 

74.2 
68.5 

9.6 

3.5 

.5 

35.4 

56.4 

14.3 

31.6 

6.2 

4.3 

6.2 

18.5 

10.2 

3.0 

6.8 

30.3 

37.7 


Per  ct. 
0.3 
.6 
.4 
.4 
.3 
.4 
.4 
.9 
.6 
.6 
.1 

2.0 
2.4 
1.2 
2.4 
3.1 

1.1 

2.0 

.4 

1.1 

1.7 

.9 

1.3 

1.1 

.8 

.7 

1.6 

1.7 

.6 

.6 

2.2 
7.2 


Fuel 
value 

per 
pound 


Calo- 
ries. 
190 
260 
295 
125 
80 
150 
230 
550 
220 
150 
50 

1,185 
1,125 
1,276 
1,280 
1,265 

1,515 
1,485 
.  385 

916 
1,386 
1,296 
2,865 
1,430 
1,146 
1,466 
1,775 
1,730 

730 
1,260 

2,625 
2,160 


o  Fruits  contain  a  certain  proportion  of  inedible  materials,  as  skin,  seeds,  etc.,  which  are  properly 
classed  as  refuse.  In  some  fruits,  as  oranges  and  prunes,  the  amount  rejected  in  eating  is  practically 
the  same  as  refuse.  In  others,  as  apples  and  pears,  more  or  less  of  the  edible  material  is  ordinarily 
rejected  with  the  sMn  and  seeds  and  other  inedible  portions.  The  edible  material  which  is  thus  thrown 
away,  and  should  properly  be  classed  with  the  waste,  is  here  classed  with  the  refuse.  The  figures  for 
refuse  here  given  represent,  as  nearly  as  can  be  ascertained,  the  quantities  ordinarily  rejected. 

b  Milk  and  shell. 

c  The  average  of  five  analyses  of  cereal  coffee  grain  is:  Water  6.2,  protein  13.3,  fat  3.4,  carbohydrates 
72.6,  and  ash  4.5  per  cent.  Only  a  portion  of  the  nutrients,  however,  enter  into  the  infusion.  The 
average  in  the  table  represents  the  available  nutrients  in  the  beverage.  Infusions  of  genuine  coffee 
and  of  tea  like  the  above  contain  practically  no  nutrients. 

PROPORTIONS  OF  NONNTJTRIENTS  IN  FOODS. 

It  will  be  interesting  to  note  some  of  the  differences  in  food  mate- 
rials as  shown  by  their  composition.  One  of  the  first  things  which 
may  be  observed  when  a  table  like  the  above  is  studied,  is  the  differ- 
ences in  the  proportions  of  nonnutrients,  i.  e.,  refuse  and  water. 
Many  kinds  of  food  as  they  are  purchased  contain  large  amounts  of 
refuse,  as  the  skin  and  bones  of  meat  and  fish,  the  skin  or  rind  and 
seeds  of  vegetables,  etc,  which  necessarily  lessen  the  proportion  of 
nutrients.  While  such  refuse  is  found  in  meats,  fish,  eggs,  fresh  vege- 
tables, and  fruits,  it  is  usually  absent  in  the  dairy  products  (milk,  but- 
ter, cheese,  etc.),  dried  vegetables,  cereal  foods  (flour,  breakfast  foods, 
etc.),  and  the  bread,  cakes,  and  other  foods  prepared  from  them.  In 
considering  the  edible  portion  we  find  that  the  amount  of  water  present 

142 


19 

also  affects  the  nutritive  value  of  food.  Water  is  necessary  to  the 
body,  and  it  is  usually  supplied  in  abundance  by  beverages,  although 
the  amount  contained  in  the  solid  food  consumed  in  a  day  is  quite 
considerable.  Water  forms  from  40  to  50  per  cent  of  the  ordinary 
cuts  of  meat;  it  is  especially  abundant  in  the  flesh  of  lean  animals, 
and  tends  to  decrease  as  fat  increases,  and  vice  versa.  It  is  even 
more  abundant  in  fresh  fish  than  in  meats,  but  in  dried  fish  there  is  of 
course  comparatively  little.  Fresh  vegetables  and  fruits  contain 
sometimes  as  much  as  80  or  90  per  cent  or  more  of  water,  while  dried 
seeds  and  the  food  materials  prepared  from  them  (beans,  peas,  meals, 
flour,  cereal  breakfast  foods,  etc.)  usually  contain,  roughly  speaking, 
from  10  to  12  per  cent  of  water.  Many  cooked  foods  contain  more 
water  than  the  raw  materials  from  which  they  are  made,  owing  to  the 
quantities  added  in  cooking.  Thus  some  thin  soups  are  little  more 
than  flavored  and  colored  water,  and  of  course  have  an  extremely 
low  nutritive  value.  In  other  cooked  foods,  notably  meat,  which 
have  been  baked,  roasted,  or  fried,  the  amount  of  water  is  diminished 
by  cooking. 

PROPORTIONS  OF  NUTRIENTS  IN  FOODS. 

The  most  important  of  the  actual  nutrients  has  been  seen  to  be  pro- 
tein. This  occurs  most  abundantly  in  animal  foods— =-meat,  fish,  eggs, 
and  dairy  products,  and  in  the  dried  legumes,  as  beans  and  peas. 
Butter  and  lard  are  exceptions  to  this  statement,  as  they  represent 
the  fat  of  milk  and  meat.  The  proportion  of  protein  present  in  meats 
and  fish  varies  greatly  with  the  kind  and  cut.  In  beef,  veal,  and  mut- 
ton it  composes  between  14  and  26  per  cent  of  the  edible  portion.  It 
is  generally  less  abundant  in  the  flesh  of  fish,  because  the  latter  is 
more  watery  than  meat.  The  fatter  the  meat  the  smaller  is  the  pro- 
portion of  protein;  lean  pork  has  less  than  beef  and  mutton,  and  fat 
pork  almost  none.  It  is  more  abundant  in  cheese  (28-38  per  cent) 
and  likewise  in  dried  beans  and  peas  (18-25  per  cent).  Protein  makes 
up,  roughly  speaking,  from  7  to  15  per  cent  of  the  cereals,  being  least 
abundant  in  rye  and  buckwheat  and  most  abundant  in  oats.  Wheat 
flour  averages  not  far  from  1 1  per  cent  and  bread  not  far  from  9  per 
cent  of  protein.  Fresh  vegetables  and  fruits  contain  almost  no  pro- 
tein, seldom  if  ever  more  than  5  and  often  only  1  per  cent  or  less. 

The  chief  sources  of  fat  in  ordinary  diet  are  the  animal  foods,  though 
some  fat  is  derived  from  vegetable  foods.  The  quantities  present  in 
meats  vary  considerably,  ranging  from  less  than  10  per  cent  in  some 
cuts  of  beef  and  veal  to  over  40  per  cent  in  a  side  of  pork  and  over  80 
per  cent  in  fat  salt  pork.  The  leaner  fish,  like  cod  and  haddock, 
usually  cojitain  almost  none,  but  in  the  fatter  kind,  like  shad,  mack- 
erel, and  notably  salmon,  there  is  often  from  5  to  10  per  cent  and  some- 
tiriicH  as  iriiich  as  15  per  cent  of  fat.     The  chemical  composition  of 


20 

salmon  is  not  unlike  that  of  lean  meat.  In  both  meat  and  fish  the 
increase  of  fat  usually  means  a  decrease  in  the  proportion  of  water,  as 
was  stated  above.  Milk  averages  about  4  per  cent  of  fat.  Butter  is, 
as  we  have  seen,  nearly  pure  fat,  and  whole  milk  cheese  may.have  any- 
where from  25  to  40  per  cent  of  fat,  according  to  the  richness  of  the 
cream  or  milk  from  which  it  is  made. 

The  olive  and  the  cotton  seed  are  rich  in  fat,  large  quantities  of  them 
being  used  annually  for  the  production  of  oils.  Most  of  our  common 
edible  nuts  also  contain  considerable  fat.  With  the  exception  of  oat- 
meal, which  contains  about  7  per  cent,  there  is  comparatively  little  fat 
in  the  cereals  in  the  form  in  which  they  are  ordinarily  purchased,  or 
in  the  dried  legumes,  while  in  the  green  vegetables  and  most  fruits  it 
is  practically  wanting. 

The  carbohydrates,  unhke  the  fats,  are  almost  entirely  absent  from 
the  animal  foods,  except  milk,  but  form  the  most  important  nutrient 
of  most  vegetable  foods.  Some  glycogen  (a  carbohydrate)  is  found  in 
the  liver  and  in  other  animal  tissues.  The  carbohydrates  make  up 
from  70  to  80  per  cent  of  the  cereals,  60  to  70  per  cent  of  the  dried 
legumes,  and  the  bulk  of  the  nutrients  of  fresh  vegetables  and  fruits. 
The  nutrients  of  sugar,  molasses,  honey,  etc.,  are,  of  course,  almost 
entirely  carbohydrates. 

Mineral  matters  occur  in  all  the  ordinary  articles  of  food.  Fresh 
meats  and  fish  contain  not  far  from  1  per  cent,  although  in  fat,  unsalted 
pork  the  quantity  may  be  as  small  as  0.1  per  cent.  Milk  contains 
about  0.7  per  cent  mineral  matters.  In  the  cereals  the  proportion 
ranges  from  about  0.3  to  over  2  per  cent,  while  in  green  vegetables 
and  fruits  it  is  usually  less  than  1  per  cent.  The  dried  legumes  con- 
tain from  3  to  4  per  cent  of  mineral  matters. 

In  brief,  then,  it  may  be  said  that  meats,  fish,  eggs,  milk,  fresh 
vegetables,  and  fruits  contain  the  most  refuse  and  water;  that  protein 
is  most  abundant  in  the  animal  foods  and  in  the  legumes  and  occurs  in 
considerable  quantities  in  the  cereals;  that  fats  occur  principally  in 
the  animal  foods ;  that  carbohydrates  are  found  almost  exclusively  in 
the  vegetable  products  and  milk ;  and  that  small  quantities  of  mineral 
matters  are  found  in  all  food  materials.  The  fuel  value  varies  within 
wide  limits,  being  greatest  in  those  materials  which  contain  the  most 
fat  and  the  least  water. 

DIGESTION,  ASSIMILATION,  AND  EXCRETION. 

' '  We  live  not  upon  what  we  eat,  but  upon  what  we  digest."  Food  as 
we  buy  it  in  the  market,  or  even  as  we  eat  it,  is  not  usually  in  condition 
to  be  made  into  body  structure  or  used  as  body  fuel.  It  must  first  go 
through  a  series  of  chemical  changes  by  what  is  called  digestion,  which 
prepare  it  to  be  absorbed,  taken  into  the  blood  and  lymph,  and  carried 

142 


21 

to  the  parts  of  the  body  where  it  is  needed.  Digestion  takes  place  in 
the  ahnientary  canal,  partly  in  the  stomach,  but  more  in  the  intestine. 
As  the  result,  the  useless  portions  are  separated  and  rejected,  while 
the  parts  which  can  serve  for  nutriment  are  changed  into  forms  in 
which  they  can  be  absorbed,  taken  into  the  circulation,  and  utilized. 

DIGESTION. 

The  alterations  which  the  food  undergoes  in  digestion  are  brought 
about  by  substances  called  ferments,  wliich  are  secreted  by  the  digest- 
ive organs.  The  saliva  in  the  mouth  has  the  power  of  changing 
insoluble  starches  into  soluble  sugar,  but  as  the  food  stays  in  the 
mouth  only  a  short  time,  there  is  generally  little  chance  for  such  action. 
The  saliva,  however,  helps  to  fit  the  food  to  be  more  easily  worked  on 
by  the  stomach.  The  gastric  juice  of  the  stomach  acts  upon  protein, 
and  the  pancreatic  juice  of  the  intestine  upon  protein,  fats,  and  carbo- 
hydrates. The  action  of  all  the  ferments  is  aided  by  the  fine  division 
of  the  food  by  chewing  and  by  the  muscular  contractions,  the  so-called 
peristaltic  action,  of  the  stomach  and  intestine.  These  latter  motions 
help  to  mix  the  digestive  juices  and  their  ferments  with  the  food. 

The  parts  of  the  food  wliich  the  digestive  juices  can  not  dissolve,  and 
which  therefore  escape  digestion,  are  periodically  given  off  by  the 
intestine.  Such  solid  excreta,  or  feces,  include  not  only  the  particles 
of  undigested  food,  but  also  the  so-called  metabolic  products,  i.  e., 
residues  of  the  digestive  juices,  bits  of  the  lining  of  the  alimentary 
canal,  etc. 

ABSORPTION  AND  ASSIMILATION. 

The  digested  food  finds  its  way  through  the  walls  of  the  alimentary 
canal,  and  at  this  time  and  later  it  undergoes  remarkable  chemical 
changes.  'When  finally  the  blood,  supplied  with  the  nutrients  of  the 
digested  food  and  freighted  with  oxygen  from  the  lungs,  is  pumped 
from  the  heart  all  over  the  body  it  is  ready  to  furnish  the  organs  and 
ti.ssues  with  the  materials  and  energy  which  they  need  for  their  pecul- 
iar functions;  at  the  same  time  it  carries  away  the  waste  which  the 
exercise  of  these  functions  has  produced.  It  is  a  characteristic  of 
living  body  tissue  that  it  can  choose  the  necessary  materials  from  the 
blood  and  build  them  into  its  own  structure.  IIow  it  does  this  is  one 
of  the  mysteries  of  physiology.  The  body,  as  we  have  learned,  has 
also  the  power  of  consuming  not  only  the  materials  of  the  food,  but  also 
parts  of  its  own  structure  for  the  production  of  muscular  work,  or  heat, 
or  to  protect  more  important  parts  from  consumption.  IIow  it  does 
this  is  another  mystery,  still  to  be  explained. 


22 

EXCRETION. 

After  the  material  has  been  thus  assimilated  and  utilized  the  result- 
ing waste  products  must  be  removed  from  the  body.  The  chemical 
elements  which  this  waste  contains  are  of  course  the  same  as  those 
making  up  the  structure  of  the  body  and  the  food — carbon,  oxygen, 
hydrogen,  nitrogen,  calcium,  phosphorus,  sulphur,  etc.  Most  of  the 
carbon  and  part  of  the  oxygen  are  given  off  from  the  lungs  as  carbon 
dioxid.  Hydrogen  unites  with  more  oxygen  to  form  water,  which  is 
passed  off  in  vapor  from  the  lungs,  in  perspiration  from  the  skin,  and 
in  urine  from  the  kidneys.  Almost  all  the  nitrogen  is  excreted  in  the 
urine.  Waste  mineral  matters  are  given  off  to  some  extent  in  the 
perspiration,  but  mainly  through  the  kidneys  and  intestines. 

APPARENT  AND  ACTTJAIi  DIGESTIBILITY. 

The  real  nutritive  value  of  a  food,  then,  depends  not  simply  on  the 
proportions  of  nutrients  which  it  contains,  but  also  on  the  amount  of 
those  nutrients  which  can  be  made  available  to  the  body  by  digestion 
for  building  material  and  for  fuel.  Part  of  the  food  eaten  escapes 
digestion  and  is  given  off  from  the  body  in  the  feces.  If  we  subtract 
the  amount  of  this  undigested  residue  from  the  total  food,  the  remain- 
der will  be  the  amoiuit  actually  digested  in  the  stomach  and  intestines 
absorbed  through  their  walls,  and  taken  into  the  circulation.  This 
difference  between  the  amounts  eaten  and  those  undigested  represents 
the  actual  digestibility  of  food.  A  part  of  the  food  taken  into  the 
circulation,  however,  is  later  returned  again  to  the  alimentary  canal 
mainly  in  the  digestive  juices  that  are  needed  for  digesting  the  food. 
The  material  thus  removed  from  circulation  and  returned  to  the  ali- 
mentary canal,  which  consists  of  so-called  metabolic  products,  is 
excreted  with  the  undigested  residue  in  the  feces.  The  remainder  of 
the  food  taken  into  the  circulation  represents  the  amount  retained  by 
the  body  for  building  material  and  for  fuel.  The  difference  between 
the  food  which  is  absorbed  and  that  which  the  body  secures,  therefore, 
is  represented  by  the  metabolic  products.  By  the  present  methods  of 
experimenting,  however,  the  portion  of  the  feces  that  consists  of 
metabolic  products  can  not  be  satisfactorily  distinguished  from  the 
imdigested  residue.  It  is  very  difficult,  therefore,  to  determine  the 
actual  digestibility,  but  comparatively  easy  to  estimate  the  apparent 
digestibility  of  food. " 

Suppose,  for  instance,  that  15  per  cent  of  the  protein  in  a  specimen 
of  bread  is  excreted,  then  85  per  cent  remains  for  the  use  of  the  body. 

alt  would  be  more  exact  to  use  different  terms  to  denote  the  apparent  digestibility  of  food 
as  distinguished  from  its  actual  digestibihty.  It  has  therefore  been  proposed  to  limit  the 
use  of  the  term  digestibihty  to  actual  digestibihty  and  employ  the  term  availabihty  when 
apparent  digestibihty,  as  ordinarily  determined  in  nutrition  investigations,  is  meant.  (See 
Connecticut  Storrs  Station  Eeport  1899,  p.  69.) 


23 

If  the  bread  has  8.4  per  cent  of  protein,  100  pounds  will  have  8.4 
pounds,  of  which  85  per  cent  or  7.1  pounds  will  be  utilized  by  the 
body.  Table  III  (p.  28)  gives  details  regarding  the  proportions  of 
digestible  nutrients  in  different  food  materials. 

EASE  AND  QUICKNESS  OF  DIGESTION. 

The  terms  digestible,  indigestible,  etc.,  as  here  used  refer  simply  to 
the  food  w-hich  is  or  is  not  available  for  the  general  nourishment  of 
the  body  after  the  process  of  digestion  is  completed.  In  common 
parlance,  however,  they  are  used  more  loosely  as  referring  to  the  ease 
and  qiiickness  of  digestion,  and  to  the  general  healthfulness  of  food. 
One  kind  of  food — bread,  for  instance — is  spoken  of  as  "simple"  and 
"digestible,"  and  another,  like  fruit  cake,  as  "rich"  and  "indigest- 
ible." There  is  often  much  practical  truth  behind  such  statements, 
though  little  is  definitely  known  concerning  the  time  or  labor  required 
to  digest  different  kinds  of  food. 

Among  the  earliest  and  most  famous  experiments  concerning  the 
time  required  for  digestion  in  the  stomach  are  those  made  by  Dr.  Wil- 
liam Beaumont,  V.  S.  A.,  between  1825  and  1833.  His  subject  was  a 
French-Canadian  trapper,  a  man  quite  normal  except  for  an  aperture 
through  the  abdomen  into  the  stomach  made  by  a  gunshot  wound,  and 
closed  only  by  a  valve  which  had  developed  over  it.  By  pressing  the 
valve  inward  the  contents  of  the  stomach  could  be  observed  or  removed 
at  will,  thus  affording  excellent  opportunity  to  study  the  action  of  the 
gastric  juice.  Dr.  Beaumont  fed  the  man  on  various  diets,  and  noted 
the  different  conditions  accompanying  each.  The  book  in  which  he 
describes  his  experiments  "contains  a  table  of  the  average  time  required 
for  the  stomach  to  digest  various  articles  of  diet,  from  which  many  of 
the  statements  still  current  concerning  the  relative  digestibility  of 
different  foods  are  taken. 

One  of  Dr.  Beaumont's  general  deductions  was  that  most  of  the 
common  foods  required  from  2  to  4  hours.     He  says  further : 

"The  time  required  for  the  digestion  of  food  is  various,  depending 
upon  the  quantity  and  quality  of  the  food,  state  of  the  stomach,  etc., 
but  the  time  ordinarily  re(|uired  for  the  disposal  of  a  moderate  meal 
of  the  fibrous  parts  of  meat,  with  bread,  etc.,  is  from  3  to  3^  hours." 

Valuable  and  interesting  as  Dr.  Beaumont's  book  undoubtedly  is,  its 
conclusions  can  not  be  taken  as  final,  because  he  does  not  state  the 
amounts  of  food  consumed.  The  science  of  nutrition  in  its  develop- 
ment has  also  shown  many  errors  in  the  reasoning.  It  should  in  jus- 
tice be  said  that  Dr.  Beaumont  recognized  the  fact  that  his  experi- 
ments had  to  do  only  with  digestion  in  the  stomach,  or  "chymifica- 

a  Williairi  B<;a)jmor)t,  T\w  Phymology  of  Digestion,  with  Experiments  on  the  Gastric  Juice. 
2d  ed.     liuriington,  Vt.,  1847. 
142 


y 


24 

tion,"  as  he  terms  it.  Furthermore,  his  experiments  have  been  often 
misquoted  and  given  a  different  interpretation  from  that  which  he 
intended. 

Food  does  not  ordinarily  pass  from  the  stomach  into  the  intestine 
imtil  it  has  been  reduced  to  a  Hquid  or  semiHquid  condition.  The 
length  of  time  required  for  different  foods  to  leave  the  stomach  has 
been  recently  studied  by  Penzoldt  with  healthy  men.  He  used  a 
stomach  tube  for  removing  the  stomach  contents  for  examination.  He 
found  that  the  amount  and  consistency  of  food  have  a  marked  influ- 
ence on  the  rate  of  digestion  in  the  stomach.  Fluids  leave  the  stomach 
more  rapidly  than  other  materials.  From  6  to  7  ounces  of  water  or 
other  common  beverages  leave  the  stomach  in  IJ  hours.  Seven  ounces 
of  boiled  milk  leave  the  stomach  in  about  2  hours.  Hot  drinks  do  not 
leave  the  stomach  more  quickly  than  cold  ones,  nor  does  the  quantity 
have  much  effect.  Solid  matter  in  solution  or  suspension  delayed  the 
passage  of  fluid  from  the  stomach  somewhat.  The  consistency  of  solid 
foods  thus  seems  to  have  more  effect  upon  digestibility  than  the 
amount  consumed.  The  quantity  eaten  increases  the  length  of  time 
the  material  remains  in  the  stomach,  but  not  proportionally. 

To  select  a  few  examples  of  the  time  required  for  foods  to  leave  the 
stomach:  Two  eggs  (raw,  poached,  or  in  the  form  of  an  omelet),  7 
ounces  sweetbreads,  10  moderate-sized  oysters,  7  ounces  white-fish  or 
3|  ounces  of  white  bread,  cauliflowers,  or  cherries,  each  left  the  stom- 
ach in  from  2  to  3  hours.  Eight  and  one-fourth  ounces  of  chicken,  9 
ounces  of  lean  beef,  6  ounces  boiled  ham,  3  J  ounces  roast  veal  or  beef- 
steak, 5J  ounces  of  coarse  bread,  boiled  rice,  carrots,  spinach,  radish, 
or  apple,  left  the  stomach  in  3  to  4  hours.  Nine  ounces  of  smoked 
tongue,  3i  ounces  smoked  beef,  9  ounces  roast  goose,  5 J  ounces  string 
beans,  or  7  ounces  peas  porridge,  left  the  stomach  in  4  to  5  hours. 

Generally  speaking,  the  most  readily  digested  animal  foods  were 
materials  of  soft  consistency.  White  meats — for  example,  chicken — 
leave  the  stomach  more  quickly  than  red  meats  or  dark  meat — for 
instance,  duck.  The  method  of  cooking  also  exerts  a  very  marked 
influence  on  stomach  digestion.  Fresh  fish  was  found  to  be  more  read- 
ily digested  than  meats. 

As  regards  vegetable  foods  in  general,  the  consistency  and  the 
amounts  of  solid  material  were  again  the  principal  factors  affecting 
the  time  required  for  digestion  in  the  stomach.  Mealy  potatoes,  for 
instance,  were  more  easily  digested  than  waxy  potatoes,  and  mashed 
potato  more  readily  than  potato  cut  up  in  pieces.  Fine  bread  was 
more  quickly  digested  than  coarse  bread.  There  was  not  much  differ- 
ence in  the  time  required  for  bread  crust,  bread  crumb,  toast,  new 
bread,  and  stale  bread  to  digest  in  the  stomach,  provided  all  were 
equally  well  chewed. 


25 

It  must  be  remembered  that  digestion  continues  in  the  intestine  and 
that  the  total  time  required  for  the  digestion  and  absorption  of  the 
nutrients  in  any  given  food  material  is  not  shown  by  such  experiments. 
They  find  their  chief  application  in  prescribing  a  diet  for  invalids,  as 
in  such  cases  it  is  often  desirable  to  require  of  the  stomach  only  a 
limited  amount  of  work. 

AGREEMENT    OF    FOOD    WITH    INDIVIDUALS. 

Digestibilit}"  is  often  confused  Avdth  another  very  different  thing, 
namely,  the  agreeing  or  disagreeing  of  food  with  the  person  who  eats 
it.  During  the  process  of  digestion  and  assimilation  the  food,  as  we 
have  seen,  undergoes  many  chemical  changes,  some  of  them  in  the 
intestines,  some  in  the  liver,  muscles,  and  other  organs.  In  these 
changes  chemical  compounds  may  b,e  formed  which  are  in  one  way  or 
another  unpleasant  and  injurious,  especially  if  they  are  not  broken 
down  (as  normally  they  are)  before  they  have  opportunity  thus  to  act. 
Some  of  the  compounds  produced  from  the  food  in  the  body  n\a,j  be 
actually  poisonous. 

Different  persons  are  differently  constituted  with  respect  to  the 
chemical  changes  which  their  food  undergoes  and  the  effect  produced, 
so  that  it  may  be  literally  true  that  "  one  man's  meat  is  another  man's 
poison."  Milk  is  for  most  people  a  very  wholesome,  digestible,  and 
nutritious  food,  but  there  are  persons  who  are  made  ill  by  drinking  it, 
and  they  should  avoid  milk.  The  writer  knows  a  boy  who  is  made 
seriously  ill  by  eating  eggs.  A  small  piece  of  sweet  cake  in  which 
eggs  have  been  used  will  cause  him  serious  trouble.  The  sickness  is 
nature's  evidence  that  eggs  are  for  him  an  unfit  article  of  food.  Some 
persons  have  to  avoid  strawberries.  Indeed,  cases  in  which  the  most 
wholesome  kinds  of  food  are  hurtful  to  individual  persons  are,  unfor- 
tunately, numerous.  Every  man  must  learn  from  his  own  experience 
what  food  agrees  with  him  and  what  does  not. 

How  much  harm  is  done  by  the  injurious  compounds  sometimes 
formed  from  ordinary  wholesome  foods  is  seldom  realized.  Physio- 
logical chemistry  is  revealing  the  fact  that  these  compounds  may  affect 
even  the  brain  and  nerves,  and  that  some  forms  of  insanity  are  caused 
by  products  formed  by  the  abnormal  transformations  of  food  and  body 
material. 

PROPORTIONS  OF  DIGESTIBLE  NUTRIENTS  IN  FOOD  MATERIALS. 

During  the  past  few  years  many  experiments  have  been  made  to 
test  the  proportions  of  nutrients  digested  from  ordinary  food  mate- 
rials. In  making  the  experiments  the  subjects  are  kept  on  a  simple 
diet,  all  the  food  and  solid  excreta  are  analyzed,  and  the  difference 
between  the  two  is  taken  to  represent  the  amount  of  food  wliich  the 


26 

body  secures  for  nutriment.  Most  of  the  subjects  have  been  people 
in  good  health;  the  great  majority  have  been  men,  but  a  few  women, 
and  especially  children. 

From  comparison  of  the  results  of  many  such  experiments  much 
interesting  knowledge  has  been  gained  of  the  relative  digestibiUty  of 
different  kinds  and  classes  of  foods. 

In  general  it  may  be  said  that  probably  most  foods  used  by  man  are 
more  completely  digested  than  is  ordinarily  supposed,  so  that  the  bulk 
of  the  intestinal  excretion  is  made  up  of  metabolic  products.  Some 
foods,  however,  contain  large  proportions  of  material  upon  which  the 
digestive  juices  can  not  so  act  as  to  make  them  capable  of  being 
absorbed.  Thus  the  outer  hull  of  the  wheat  grain  contains  woody 
substance  which  passes  through  the  alimentary  canal  of  man  undi- 
gested, though  animals,  like  cows  and  sheep,  can  digest  a  large  part 
of  it. 

It  has  been  found  that  in  the  total  food  of  an  ordinary  mixed  diet,  on 
the  average,  about  92  per  cent  of  the  protein,  95  per  cent  of  the  fats, 
and  97  per  cent  of  the  carbohydrates  are  retained  by  the  body.  In  the 
average  proportions  in  which  the  different  animal  and  vegetable  foods 
are  combined  in  the  diet  about  97  per  cent  of  the  protein,  95  per  cent 
of  the  fats,  and  98  per  cent  of  the  carbohydrates  of  the  animal  foods 
are  digested,  while  only  84  per  cent  of  the  protein,  90  per  cent  of  the 
fats,  and  97  per  cent  of  the  carbohydrates  of  the  vegetable  foods  are 
digested.  Animal  foods,  therefore,  seem  to  have  a  greater  digestibility 
than  vegetable,  especially  as  regards  the  protein  they  contain.  The 
digestibility  of  a  given  article  of  food  depends,  of  course,  upon  the 
digestibility  of  the  different  classes  of  nutrients  and  upon  the  relative 
proportion  in  which  these  nutrients  occur.  Thus,  of  two  cereals  con- 
taining about  the  same  amount  of  dry  matter,  but  with  different  pro- 
portions of  protein  and  carbohydrates,  the  one  with  the  larger  propor- 
tion of  the  less  digestible  protein  and  the  smaller  proportion  of  the 
more  digestible  carbohydrates  will  be,  on  the  whole,  less  completely 
digested. 

The  figures  given  in  Table  I  (p.  16)  do  not,  then,  represent  the 
nutrients  actually  available  for  the  uses  of  the  body,  but  those  con- 
tained in  the  food  before  it  is  eaten.  The  nutrients  actually  available 
must  be  calculated  from  the  total  amounts  shown  in  the  table  by  use 
of  the  proper  factors  for  digestibility.  Thus  if  53.1  per  cent  of  bread 
is  carbohydrates  the  percentage  of  carbohydrates  which  the  body  will 
obtain  from  a  given  amount  of  bread  will  be  98  per  cent  of  53.1,  or 
52  per  cent  of  the  weight  of  the  bread.  Similarly  the  fuel  value  given 
is  not  the  heat  of  combustion  of  the  food  consumed,  but  that  of  the 
nutrients  actually  oxidized  in  the  body.  This  fuel  value  may  be  calcu- 
lated from  the  proportions  of  digestible  nutrients  and  the  fuel  values 
of  each  as  learned  by  experiment. 

142 


27 

The  proportions  of  the  several  nutrients  which  the  body  retains  for 
its  use  are  commonly  called  percentages  or  coefficients  of  digestibility .  <» 

From  the  results  of  a  large  amount  of  experimenting  it  appears  that 
the  coefficients  of  digestibility  and  the  fuel  value  per  pound  of  different 
food  materials  or  groups  of  materials  are  approximately  as  follows: 

Tabi-e  II. — Coefficients  of  digestibility  and  fuel  value  per  pound  of  nutrients  in  different 

groups  of  food  materials. 


Kind  of  food. 


Meats  and  fish 

Eggs • 

Dairy  products 

Animal  food  (of  mixed  diet) 

Cereals 

Legumes  (dried) 

Sugars 

Starches 

Vegetables 

Fruits 

Vegetable  foods  (of  mixed  diet) . 
Total  food  (of  mixed  diet) 


Protein. 


Digesti- 
blUty. 


Per  cent. 
97 
97 
97 
97 
85 
78 


Fuel 

value  per 

pound. 


Calories. 
1,940 
1,980 
1,940 
•  1,940 
1,750 
1,570 


1,410 
1,520 
1.840 
1,820 


Fat. 


Digesti- 
bility. 


Per  cent. 
95 
95 
95 
95 
90 
90 


Fuel 

value  per 

pound. 


Calories. 
4,040 
4,090 
3,990 
4,050 
3,800 
3,800 


3,800 
3,800 
3,800 
4,050 


Carbohydrates. 


Digesti- 
bility. 


Per  cent. 
98 
98 
98 
98 
98 
97 
98 
98 
95 
90 
97 
97 


Fuel 
value  per 
pound. 


Calories. 
1,730 
1,730 
1,730 
1,730 
1,860 
1,840 
1,750 
1,860 
1,800 
1,630 
1,820 
1,820 


The  figures  of  Table  III  (p.  28)  show  the  digestible  nutrients  and 
available  energy  in  a  number  of  common  food  materials,  as  computed 
from  the  figures  in  Table  I,  by  use  of  the  factors  given  in  Table  II. 
The  further  assumption  is  made  that  75  per  cent  of  the  ash  is  digesti- 
ble. The  figures  in  the  third  column  of  Table  III  show  the  total 
quantity  of  indigestible  nutrients.  The  term  used  as  the  heading  of 
the  last  column,  ''nutritive  ratio,"  or,  as  it  is  sometimes  and  perhaps 
more  accurately  called,  "nutrient  ratio,"  requires  a  word  of  explana- 
tion. The  term  nutritive  ratio  is  used  to  express  the  ratio  of  digesti- 
ble protein  to  digestible  fuel  ingredients  (fats  and  carbohydrates)  in 
any  food  material  or  diet.  In  calculating  this  ratio  1  pound  of  fat  is 
taken  as  equivalent  to  2\  pounds  of  carbohydrates — this  being 
approximately  the  ratio  of  their  fuel  values — so  that  the  nutritive 
ratio  is  actually  that  of  the  protein  to  the  carbohydrates  plus  2 J 
times  the  fat. 


"It  should  be  understood  that  the  terms  "digestibility"  and  "digestible  nutrients  "and 
"wjefRcients  of  digestibility,"  a.s  u.sed  in  the  following  tables  and  the  accompanying  expla- 
nations, refer  to  apparent  digestibility  (see  p.  22). 

142 


28 


Table    III. — Nutrients   and  energy   of  digestible   portion   of   some   common  foods, 

nutritive  ratios. 


with 


Kind  of  food  materials. 


ANIMAL   FOOD. 

Beef,  fresh: 

Chuck,  ribs 

-Lom,  medium 

Ribs '. 

Round,  medium 

Shoulder  and  clod 

Beef,  dried  and  smoked 

Veal: 

Cutlets,  round 

Leg 

Mutton: 

Leg 

Loin 

Pork,  fresh: 

Loin,  chops 

Ham 

Pork,  salted  and  smoked: 

Bacon 

Ham 

Salt,  fat 

Poultry: 

Fowl 

Turkey 

Fish,  fresh: 

Cod,  dressed 

Mackerel 

Shellfish: 

Oysters,  solids 

Fish,  preserved  and  canned: 

Cod,  salt 

Salmon,  canned 

Eggs,  uncooked 

Dairy  products: 

Whole  milk 

Skim  milk 

Cream 

Butter 


VEGETABLE   FOOD. 

Cereals,  etc.: 

Corn  meal 

Oat  breakfast  food 

Rye  flour 

Rice 

Wheat  flour,  patent 
process 

Wheat  breakfast  food. . 
Bread,  etc.: 

Bread,  white  wheat 

Crackers,  cream 

Vegetables: 

Beans,  white,  dried .  . . . 

Beets,  fresh 

Cabbage 

Potatoes 

Squash 

Sweet  potatoes,  fresh... 

Tomatoes 

Fruits: 

Apples 

Bananas 

Grapes 

Oranges 

Strawberries 


Per 

cent. 
16.3 
13.3 
20.8 

7.2 
16.4 

4.7 

3.4 
14.2 

18.4 
16 

19.7 
10.7 

7.7 
13.6 


25.9 
22.7 


29.9 
44.7 


24.9 
'ii.'2' 


Per 
cent. 
52.6 
52.5 
43.8 
60.7 
56.8 
53.7 

68.3 
60.1 

51.2 
42 

41.8 


17.4 
34.8 
7.9 

47.1 
42.4 

58.5 
40.4 

88.3 

40.2 
63.5 
65.5 

87 

90.5 
74 
11 


12.5 
7.8 
12.9 
12.3 

12 
9.6 

35.3 

6.8 

12.6 

70 

77.7 

62.6 

44.2 

55.2 

94.3 

63.3 
48.9 

58 

63.4 

85.9 


Per 
cent. 
1.4 
1.6 
1.8 
1.4 
1.2 
4.5 

1.2 
1.1 


1.8 
1.9 

4.4 
3.1 
6.4 

1.2 

1.6 


.6 

5.1 

1.9 
1.1 

.5 

.3 

1.1 

4.9 


3.3 
5.1 
2.9 
2.9 

3.4 
3.8 

2.9 

4.5 


.6 
1.2 

.4 
1.6 

.5 

1.2 

1.6 

1.7 

1 

1 


Digestible  nutrients. 


Per 

cent. 
15 
15.6 
13.5 
18.4 
15.9 
25.6 

19.5 
15 

14.6 
13.1 

13 
13.1 


13.8 
1.8 


13.3 
15.6 


10.8 
9.9 


15.5 
21.1 
12.7 


3.2 
3.3 
2.4 
1 


7.8 
14.2 
5.8 
6.8 

9.7 
10.3 

7.8 
8.2 

17.5 
1.1 
1.2 
1.5 

.6 
1.2 

.7 


Per 
cent. 
14.3 
16.6 
20 
12.2 
9.3 
6.6 

7.1 
7.5 

14 
26.9 

23 
24.6 

59.1 
31.7 
81.  9 

11.7 
17.5 


4 
1.2 


.4 
11.5 


3.8 

.3 

17.6 


1.7 
6.6 


.9 
1.6 

1.2 
10.9 

1.6 
.1 
.2 
.1 
.2 
.5 
.4 

.3 
.4 
1.1 
.1 
.5 


Per 

cent. 


5 

5.1 

4.5 


73.9 
64.9 

77.1 
77.4 

73.6 
73.7 


68.3 

57.8 
7.3 
4.6 

14 
4.3 

20.8 
3.7 

9.7 
12.9 
13 
7.7 
6.3 


Per 
cent. 
0.6 

.7 
.5 
.8 
.7 
5.5 

Calo- 
ries. 
910 
1,025 
1,135 
890 
715 
790 

.8 
.7 

695 
625 

.6 
.5 

1,415 

.6 
.6 

1,245 
1,320 

3.1 
3.2 
2.9 

2,720 
1,635 
3,555 

.  a 

.6 

766 
1,060 

.6 
.5 

220 
370 

.8 

225 

13.9 
2 

".7 

325 
915 
635 

.5 

.5 

.4 

2.3 

310 

165 

865 

3,410 

.8 

1.4 

.5 

.3 

1,640 
1,800 
1,620 
1,625 

.4 

1 

1,635 
1,680 

.8 
1.3 

1,200 
1,925 

2.6 
.7 
.7 
.6 
.3 
.7 
.4 

1,620 
160 
115 
295 
100 
440 
95 

.2 
.6 
.3 
.3 

.5 

190 
260 
295 
150 
150 

142 


29 


The  principal  data  included  in  Table  III  are  shown  in  graphic  form 
in  Chart  1. 

Chart  1.— COMPOSITION  OF  FOOD  IvIATERIALS 

Nutritive  ingredients,  refuse,  andfu£l  value. 

DtcftJtihle        miiyitTtts InoUqtttthU  luUntnts       fiorv  nutntnh 

Refujt 


Carbo-       MinercU- 
bydU-citej     niccUtrt 


Muscle 
making. 


Fuel  ingredients. 


30 

It  is  to  be  observed  that  the  values  given  in  Table  III,  like  those  of 
Table  I,  represent  averages.  Different  specimens  of  the  same  kind  of 
food  material  differ  in  composition,  digestibility,  and  nutritive  value. 
Materials  which  are  grouped  in  the  same  class  may  also  differ  more  or 
less  in  this  respect.  Thus  potatoes,  turnips,  cabbage,  or  even  different 
specimens  of  the  same  vegetable,  may  differ  in  the  proportions  of 
nutrients  digested.  The  figures  in  Table  III,  therefore,  are  to  be 
taken  as  only  approximate  values. 

PREPARATION  OF  FOOD— COOKING. 

The  cooking  of  food  has  much  to  do  with  its  nutritive  value.  Many  - 
articles  which,  owing  to  their  mechanical  condition  or  other  cause,  are 
quite  unfit  for  nourishment  when  raw  are  very  nutritious  when  cooked. 
It  is  also  a  matter  of  common  experience  that  a  well-cooked  food  is 
wholesome  and  appetizing,  while  the  same  material  badly  cooked  is 
unpalatable.  There  are  three  chief  purposes  of  cooking.  The  first 
is  to  change  the  mechanical  condition  so  that  the  digestive  juices  can 
act  upon  the  food  more  freely.  Heating  often  changes  the  structure 
of  food  materials  very  materially,  so  that  they  are  more  easily  chewed 
and  more  easily  and  thoroughly  digested.  The  second  is  to  make  it 
more  appetizing  by  improving  the  appearance  or  flavor,  or  both. 
Food  which  is  attractive  to  the  taste  quickens  the  flow  of  saliva  and 
other  digestive  juices,  and  thus  digestion  is  aided.  The  third  is  to 
kill  by  heat  any  disease  germs,  parasites,  or  other  dangerous  organ- 
isms it  may  contain.  This  is  often  a  very  important  matter,  and 
applies  to  both  animal  and  vegetable  foods. 

The  cooking  of  meats  develops  the  pleasing  taste  and  odor  of 
extractives  and  that  due  to  the  browned  fat  and  tissues  and  softens 
and  loosens  the  protein  (gelatinoids)  of  the  connective  tissues,  and 
thus  makes  the  meat  more  tender.  Extreme  heat,  however,  tends  to 
coagulate  and  harden  the  albuminoids  of  the  lean  portions,  and  also 
weakens  the  flavor  of  extractives.  If  the  heating  is  carried  too  far  a 
burned  or  charred  product  of  bad  flavor  results. 

Meats  lose  weight  in  cooking.  A  small  part  of  this  is  due  to  escape 
of  meat  juices  and  fat,  but  the  chief  part  of  the  material  lost  is  simply 
water.  The  nutritive  value  of  a  meat  soup  depends  upon  the  sub- 
stances which  are  dissolved  out  of  the  meat,  bones,  and  gristle  by  the 
water.  In  ordinary  meat  broth  these  consist  almost  wholly  of  extract- 
ives and  salts,  which  are  very  agreeable  and  often  most  useful  as  stimu- 
lants, but  have  little  or  no  value  as  actual  nutriment,  since  they  neither 
build  tissue  nor  yield  energy.  The  principles  which  underUe  the  cook- 
ing of  fish  are  essentially  the  same  as  with  meats. 

In  many  vegetables  the  valuable  carbohydrates,  chiefly  microscopic 
starch  grains,  are  contained  in  tiny  cells  with  thick  walls  on  which  the 


31 

digestive  juices  have  little  effect.  The  heat  of  cooking,  especially 
with  the  aid  of  water,  ruptures  these  walls  and  also  makes  the  starch 
more  soluble.  The  heat  also  caramelizes  a  portion  of  the  carbohy- 
drates and  produces  agreeable  flavors  in  this  and  other  ways. 

In  breads,  cakes,  pastry,  and  other  foods  prepared  from  flour,  the 
aim  is  to  make  a  palatable  and  lighter  porous  substance  more  easily 
broken  up  in  the  alimentary  canal  than  the  raw  materials  could  be. 
Sometimes  this  is  accomplished  simply  by  means  of  water  and  heat. 
The  heat  changes  part  of  the  water  in  the  dough  into  steam,  which,  in 
trying  to  escape,  forces  the  particles  of  dough  apart.  The  protein 
(gluten)  of  the  flour  stiffens  about  the  tiny  bubbles  thus  formed  and 
the  mass  remains  porous  even  after  the  steam  has  escaped.  More 
often,  however,  other  things  are  used  to  "raise"  the  dough — such  as 
yeast  and  baking  powder.  The  baking  powder  gives  off  the  gas 
carbon  dioxid  and  the  yeast  causes  fermentation  in  the  dough  by 
which  carbon  dioxid  is  produced.  This  acts  as  the  steam  does,  only 
much  more  powerfully.  When  beaten  eggs  are  used,  the  albumen 
incloses  air  in  bubbles  which  expand,  and  the  walls  stiffen  with  the 
heat  and  thus  render  the  food  porous. 

Scrupulous  neatness  should  always  be  observed  in  keeping,  hand- 
ling, and  serving  food.  If  ever  cleanliness  is  desirable,  it  must  be  in 
the  things  we  eat,  and  every  care  should  be  taken  to  insure  it  for  the 
sake  of  health  as  well  as  of  decency.  Cleanliness  in  this  connection 
means  not  only  absence  of  visible  dirt,  but  freedom  from  undesirable 
bacteria  and  other  minute  organisms,  and  from  worms  and  other  para- 
sites. If  food,  raw  or  cooked,  is  kept  in  dirty  places,  peddled  from 
dirty  carts,  prepared  in  dirty  rooms  and  in  dirty  dishes,  or  exposed  to 
foul  air,  disease  germs  and  other  offensive  and  dangerous  substances 
can  easily  get  in. 

Food  and  drink  may,  in  fact,  be  very  dangerous  purveyors  of  dis- 
ease. The  bacteria  of  typhoid  fever  sometimes  find  their  way  into 
drinking  water,  and  those  of  typhoid  and  scarlet  fevers  and  diphtheria 
into  milk,  and  bring  sickness  and  death  to  large  numbers  of  people. 
Oysters  which  are  taken  from  the  salt  water  where  they  grow  and 
"floated"  for  a  short  time  in  brackish  water  near  the  mouth  of  a 
stream,  have  been  known  to  be  infected  by  typhoid  fever  germs 
brought  into  the  stream  by  the  sewage  from  houses  where  the  dejec- 
tions from  patients  had  been  thrown  into  the  drains.  Celery  or  let- 
tuce grown  in  soil  containing  typhoid  germs  has  been  thought  to  con- 
vey this  disease. 

Food  materials  may  also  contain  parasites,  like  tapeworms  in  beef, 
pork,  and  mutton,  and  trichinae  in  pork,  which  are  often  injurious 
and  sometimes  deadly  in  their  effect.  This  danger  is  not  confined  to 
animal  foods.     Vegetables  and  fruits  may  become  contaminated  with 

142 


32 

eggs  of  numerous  parasites  from  the  fertilizers  applied  to  them.  Kaw 
fruits  and  vegetables  should  always  be  Terr  thoroughly  washed  before 
seiwing  if  there  is  any  doubt  as  to  their  cleanliness.  If  the  food  is 
sufficiently  heated  in  cooking,  all  organisms  are  killed. 

Sometimes  food  midergoes  decomposition  in  which  injurious  chem- 
ical compounds,  so-called  ptomaines,  are  formed.  Poisoning  by 
cheese,  ice  cream,  preserved  hsh,  canned  meats,  and  the  like  has  been 
caused  in  this  way.  The  ptomaines  often  withstand  the  heat  of 
cooking. 

In  some  ceases  it  ha^  been  foimd  that  foods  are  adulterated  ^^ith 
compotmds  injimous  to  health:  btit  sophistication  in  which  harmless 
articles  of  inferior  cost  or  quahty  are  added  is  more  common. 

Dainty  ways  of  serving  food  have  a  tisefulness  beyond  their  esthetic 
value.  Everyone  knows  that  a  feeble  appetite  is  often  tempted  by  a 
tastefully  garnished  dish,  when  the  same  material  carelessly  served 
would  seem  quite  tmpalatable.  Fi.u"thermore,  many  cheap  articles 
and  •'•  left-overs "'  when  well  seasoned  and  attractively  served  may  be 
just  as  appetizing  as  dearer  ones,  and  will  usually  be  foimd  quite  as 
nutritiotis. 

DIETAEIES  AlfD  DIETAEY  STANDAEDS. 

The  information  gained  from  a  study  of  the  composition  and  nutri- 
tive value  of  foods  may  be  turned  to  practical  accoimt  by  using  it  in 
planning  diets  for  different  individuals  or  classes  of  individuals  or  in 
estimating  the  true  nutririve  value  of  the  food  acttially  constmied  by 
families  or  individuals.  By  comparing  the  results  of  many  such  inves- 
tigations with  the  results  of  acctu"ate  physiological  experimenting  it  is 
possible  to  learn  about  how  much  of  each  of  the  nutrients  of  common 
foods  is  needed  by  persons  of  different  occupations  and  habits  of  hfe, 
and  from  this  to  compute  standards  representing  the  average  require- 
ments for  food  of  such  persons. 

3so:thods  of  making  dietary  studies. 

During  the  last  twenty  years  much  of  this  practical  appHcation  of 
the  chemistjy  of  food  has  been  made  in  the  study  of  actual  dietaries. 
Much  work  of  this  kind  has  been  done  in  England,  Germany,  Italy, 
Etissia.  Sweden,  and  elsewhere  in  Etirope,  and  in  Japan  and  other 
oriental  countries.  "VTithin  the  past  dozen  years  extensive  sttidies 
have  been  made  iu  the  United  States.  The  simplest  way  of  making 
stich  inquiries  is  to  find  otit  what  kinds  and  quantities  of  food  are  used 
dming  a  given  period  in  the  household  in  which  the  study  is  made; 
to  estimate  the  amounts  of  variotis  nutrients  which  the  different  mate- 
rials contain  by  means  of  figures  given  for  the  average  composition  of 
the  various  articles  in  tables,  like  Table  I  (p.  16),  and  then  to  calcu- 

142 


33 

late  the  cost  and  amount  of  nutrients  for  each  person.  There  are, 
however,  several  chances  for  error  in  such  a  method.  In  the  first 
place,  since  different  specimens  of  the  same  kind  of  food  vary  greatly 
in  composition,  it  is  often  inaccurate  to  estimate  the  nutrients  of  one 
specimen  from  figures  representing  the  average  composition.  Accord- 
ingly, in  the  more  careful  dietary  studies,  the  composition  of  the  food 
is  determined  by  analyzing  samples  of  materials  actually  used.  Again, 
this  method  assumes  that  all  the  food  is  really  consumed,  whereas  it 
is  very  plain  that  frequently  no  small  portion  is  wasted  in  the  kitchen 
or  at  the  table.  This  difficulty  is  usually  met  by  measuring  and  com- 
puting the  amounts  of  nutrients  in  the  waste  and  sometimes  by  analyz- 
ing samples  of  it. 

In  preparing  the  results  of  dietary  studies  so  that  different  studies 
may  be  compared,  another  difficulty  appears.  For  example,  in  a  fam- 
ily consisting  of  father,  mother,  and  two  children  of  different  ages  the 
amount  of  food  taken  by  each  is  by  no  means  the  same,  and  it  would 
be  quite  incorrect  to  divide  the  whole  amounts  consumed  by  four  and 
rail  the  result  the  amount  used  per  person.  Men,  as  a  rule,  cat  more 
than  women,  women  more  than  young  children,  and  persons  of  active 
habits  more  than  those  who  take  little  muscular  exercise.  A  coal 
heaver,  who  is  constantly  using  up  nutritive  material  of  muscular 
tissue  to  supply  the  energy  refjuired  for  his  severe  muscular  work, 
needs  a  diet  with  more  protein  and  higher  fuel  value  than  a  book- 
keeper who  sits  at  a  desk  all  day.  It  is  ordinarily  estimated  that,  as 
compared  with  a  man  at  moderate  or  light  work,  a  woman  under  simi- 
lar conditions  needs  0.8  as  much  food,  and  children  amounts  varying 
with  their  ages,  and  such  figures  are  used  to  reduce  the  statistics  of  a 
dietary  to  the  standard  of  one  man  at  moderate  work.  The  various 
factors  commonly  used  in  the  United  States  in  computing  the  results 
of  dietary  studies  are  as  follows: 

Factors  wied  in  calculating  meals  consumed  in  dietary  studte/i. 

Man  at  hard  muscular  work  requires  1.2  the  food  of  a  man  at  moderately  active  muscular 

work. 
Man  with  light  muscular  work  and  hoy  l.S-16  years  old  require  0.0  I  lie  food  of  a  man  at 

moderately  active  muscular  work. 
Man  at  sedentary  occupation,  woman  at  moderately  active  work,  hoy  IS-H,  and  girl  ir>-10 

years  old  require  0.8  the  food  of  a  man  at  moderately  active  mus*;ular  work. 
Woman  at  light  work,  iKiy  12,  and  girl  13-14  years  old  require  0.7  the  food  of  a  man  at 

mo<lerately  active  mu.scular  work. 
Boy  10-11  and  girl  10-12  years  old  require  O.G  tlie  food  of  a  man  at  moderately  active 

muscular  work. 
Child  Cy-O  years  old  requires  Of}  the  food  of  a  man  at  moderately  active  muscular  work. 
Cliild  2-5  years  old  requires  0.4  the  food  of  a  man  at  moderately  iictive  muscular  work. 
Child  under  2  years  old  requires  0.3  the  food  of  a  man  at  moderately  active  muscular  work. 


34 

These  factors  are  based  in  part  upon  experimental  data  and  in  part 
upon  arbitrary  assumptions.  They  are  subject  to  revision  when 
experimental  evidence  shall  warrant  more  definite  conclusions. 

In  making  dietary  studies  in  this  country  blanks  are  usually  pre- 
pared to  be  filled  out  with  statistics  of  the  amounts,  kinds,  cost,  and 
estimated  nutrients  of  the  food  purchased,  wasted,  and  actually  con- 
sumed, and  information  concerning  the  number,  sex,  age,  and  occu- 
pation of  the  persons  for  whom  the  food  is  provided.  If  further  data 
are  gathered  concerning  the  health,  nationality,  income,  and  general 
conditions  of  the  individuals  of  families,  the  results  of  such  inquiries 
have  a  wider  physiological  and  sociological  bearing.  These  supple- 
mentary statistics  have  been  collected  in  considerable  detail  in  late 
studies  in  the  United  States. 

AMERICAN  AND   EUROPEAN    DIETARIES  AND  DIETARY  STAND- 
ARDS. 

Many  interesting  things  come  to  light  on  comparing  the  dietaries  of 
persons  with  different  occupations  and  incomes  and  performing  differ- 
ent amounts  of  muscular  work.  A  comparison  of  the  dietaries  of  the 
inhabitants  of  different  countries  is  also  interesting.  Such  compari- 
sons are  made  in  the  following  table,  which  includes  as  well  the  com- 
monly accepted  dietary  standards.  The  figures  show  the  quantities 
of  both  total  and  available  nutrients.  The  fuel  value  represents  the 
actual  amount  of  available  energy,  and  may  be  computed  from  either 
the  total  or  the  digestible  nutrients  by  use  of  appropriate  factors. " 

Table  IV. — Food  consumption  of  persons  in  different  circumstances,  and  proposed  dietary 

standards. 

[Quantities  per  man  per  day.] 


Num- 
ber of 
stud- 

Actually eaten. 

Digestible. 

ies 
in- 
clud- 
ed in 

Pro- 
tein. 

Fat. 

Carbo- 
hy- 
drates. 

Pro- 
tein. 

Fat. 

Carbo- 
hy- 
drates. 

Fuel 
value. 

aver- 

ages. 

7 
3 

Gms. 
155 
186 

6ms. 
177 
186 

Gms. 
440 
651 

Gms. 
143 
171 

Gms. 
168 
177 

Gms. 
427 
631 

Calo- 
ries. 
3,955 
6,005 

2 
1 
5 

226 
139 
189 

354 
113 
110 

634 
677 
714 

208 
128 
174 

336 
107 
104 

615 
657 
693 

6,590 
4,270 
4,590 

10 

14 

97 
103 

130 
150 

467 
402 

89 
95 

124 
143 

453 
390 

3,415 
3,355 

Nutri- 
tive 
ratio. 


PERSONS  WITH  ACTIVE  -WOEK. 


Rowing  clubs  in  New  England 

Bicyclists  in  New  York 

Football  teams  in  Connecticut  and 

California 

Prussian  machinists 

Swedish  mechanics 


5.6 
6 

6.6 

7 

5.3 


PERSONS  WITH   ORDINARY  WORK. 

Farmers'  families  in  eastern  United 
States 

Mechanics'  families  in  United  States . 

"These  factors  are  as  follows:  For  each  gram  of  total  nutrients,  protein  4.0,  fat  8.9,  and  carbohy- 
drates 4.0  calories.  For  each  gram  of  digestible  nutrients,  protein  4.4,  fat  9.4,  and  carbohydrates  4.1 
calories. 


8.2 
7.5 


35 


Table  IV.- 


-Food  consumption  of  persons  in,  different  circumstances,  otuJ  proposed  dietary 
standards — Continued. 


PEESONS  WITH    ORDINARY  WORK — 

continued. 

Laborers'  families  in  large  cities  of 
United  States 

Laborers'  families  in  United  States 
(more  comfortable  circumstances) . . 

Russian  peasants 

Swedish  mechanics 


PROFESSIONAL  MEN. 

Lawyers,    teachers,   etc.,   in    United 

States 

College  clubs  in  United  States 

German  physicians 

Japanese  professor 

MEN  WITH  LITTLE  OR  NO  EXERCISE. 

Men  (American)  in  respiration  calo- 
rimeter   

Men  (German)  in  respiration  appa- 
ratus   

PERSONS  IN  DESTITUTE  CIRCUMSTANCES, 

Poor  families  in  Xew  York  City 

Laborers'  families  in  Pittsburg,  Pa. . . 

German  laborer's  family 

Italian  mechanics 

MISCELLANEOUS. 

Neero  families  in  Alabama  and  Vir- 


I  talian  families  in  Chicago 

French  Canadians  in  Chicago 

Bohemian  families  in  Chicago 

Inhabitants  Java  village,  Columbian 

Exposition,  1893 

Russian  Jews  in  Chicago 

Mexican  families  in  New  Mexico 

Chinese  dentist  in  Califomia 

Chinese  laundryman  in  California 

Chinese  farm  laborer  in  Califomia 

United  States  Army  ration,  peace 

German  army  ration,  peace , 


DIETAEV  STANDARDS. 


Man  at  hard  work  (Volt) 

Man  at  moderate  work  (Voit) , 

Man  with  very  hard  muscular  work 

( A  twater) 

Man  with  hard  muscular  work  (At- 

watcr) 

Man  with  moderately  active  muscular 

work  (\  twater) , 

Man  with  liKht  to  moderate  muscular 

work  (.\ twater) 

Man  at  "fledentary"  or  woman  with 

mfKJerately  active  work  (Atwatcr).. 
Woman  at  light  to  moderate  muscular 

work,    or   man    without   muscular 

exercue  (Atwater) 


Num 
ber  of 
stud- 
ies 
in- 
clud- 
ed in 
aver- 
ages. 


Actually  eaten. 


Pro- 
tein. 


Gms. 
101 

120 
129 
134 


104 
107 
131 
123 


112 
127 


86 
103 

118 
115 

66 
137 

94 
115 
135 
144 
120 
114 


145 
118 

175 

150 

125 

112 

100 

90 


Fat. 


Oms. 
116 

147 
33 
79 


125 
148 
95 
21 


145 
111 
158 
101 

19 
103 

71 
113 

76 

95 
161 

39 


100 
56 

(«) 

(«) 

(») 

(<•) 

(«) 

C) 


Carbo- 

hy- 
drates. 


Oms. 
344 

534 
589 
523 


423 
459 
327 
416 


305 
302 


407 
308 
287 
396 


440 
391 
345 
360 

254 
418 
613 
289 
566 
640 
454 


450 
500 

(») 

(«) 

(») 

(«) 

(«) 

(«) 


Digestible. 


Pro- 
tein. 


Oms. 
93 

110 
119 
123 


121 
113 


103 
117 


70 


79 
95 
109 
106 

61 
126 

86 
106 
124 
132 
110 
105 


133 
109 

101 

K« 

11.'') 

103 

92 


Fat. 


Oms. 
110 

140 
31 
75 


119 
141 
90 
19 


138 
105 
150 
96 


67 
107 

72 

90 
153 

37 


95 
53 

(«) 

C) 
C) 

(«) 
(«) 

C) 


Carbo- 

hy- 
drates. 


Gms. 
334 

518 
571 
507 


410 
445 
317 
403 


296 
293 


395 
299 
278 
384 


427 
379 
335 
349 

246 
405 
595 
280 
549 
621 
440 
466 


437 

485 

(«) 
(«) 
(«) 
(«) 
(«) 

C) 


Fuel 
value. 


Calo- 
ries. 
2,810 

3,925 
3,105 
3,330 


3,220 
3,580 
2,680 
2,345 


2,380 
2,430 


2,845 
2,400 
1,640 
2,225 


3,395 

2,9a5 
3,  'ifiO 
2,800 

1,4.W 
3,135 
3,4t» 
2,620 
3, 4S0 
3,9.S0 
3, 730 
2,  TIT, 


3,270 
2,i)(L') 

■1,  VM 
3,  100 
3,  (no 
2,700 

2, 4.'">0 


aFata  and  carbohydrates  in  BUfficient  amounta  to  furnish,  together  with  tho  protein,  the  indicated 
amount  of  energy. 

142 


36 

The  dietary  standards «  given  in  the  table  (pp.  34,  35)  are  based,  as 
far  as  possible,  upon  the  results  of  observation  and  experiment,  but  are 
at  best  general  estimates  and  not  guides  to  be  blindly  followed.  They 
are  subject  to  revision  in  the  light  of  further  experimental  evidence.  It 
will  be  observed  that  the  amounts  of  energy  provided  in  the  American 
standards  are  somewhat  larger  than  in  the  European  standards  (Voit's) . 
This  corresponds  to  the  observed  fact  that  people  in  this  country,  more 
especially  the  working  people,  are  as  a  rule  better  fed  and  do  more  work 
than  those  of  corresponding  classes  in  Europe.  The  quantities  of  pro- 
tein in  these  standards  are  larger  in  proportion  to  the  fuel  ingredi- 
ents— that  is,  the  nutritive  ratio  is  narrower — than  is  found  in  the 
average  American  diet.  In  this  respect  the  standards  agree  more 
nearly  with  the  diet  of  well-to-do  people  in  Europe.  It  is  believed 
that  the  larger  amount  of  protein  represents  rather  more  nearly  a 
physiological  ration  than  do  the  proportions  as  found  in  the  majority 
of  actual  dietaries. 

The  results  of  a  large  amount  of  experimental  investigation  bear  out 
the  common  belief  that  the  American,  as  a  rule,  uses  more  food  than  the 
European  of  the  same  class.  The  character  of  the  food  is,  however, 
quite  different.  The  poor  peasants  of  Russia  and  northern  Germany 
live  chiefly  upon  rye  bread,  potatoes,  and  some  sort  of  fat.  In  Italy 
maize,  chestnuts,  and  acorn  meal  form  an  important  item  in  the  diet  of 
a  considerable  portion  of  the  poorer  population.  The  use  of  meat  among 
the  working  population  of  most  European  and  Asiatic  countries  is  very 
much  less  general  than  in  America,  because  its  cost  is  prohibitive. 

In  the  majority  of  European  dietaries  the  fats  occur  in  relatively 
smaller  and  carbohydrates  in  relatively  larger  amounts  than  in  Ameri- 
can dietaries.  This  is  probably  due  in  large  measure  to  the  smaller 
quantities  of  meats  used  in  the  former  dietaries. 

Among  the  more  scantily  nourished  peoples  of  the  globe  are  the 
poor  of  India  and  China.  They  live  largely  on  rice  and  other  cereals 
and  vegetables,  with  more  or  less  of  pulse  and  other  legumes,  and 
often  on  quantities  which  to  the  ordinary  American  would  seem  little 
more  than  a  starvation  diet. 

A  close  examination  of  the  detailed  statistics  from  which  those  of 
Table  III  (p.  28)  have  been  selected  shows  that,  although  there  may  be 
occasional  wide  variations  between  two  individuals  of  a  given  class  in 
respect  to  the  total  amounts  of  food  eaten,  yet,  on  the  whole,  through 
extended  periods,  there  are  not  unusually  large  variations  in  amounts  of 
protein  or  energy  in  the  food  consumed  by  different  individuals  of  the 
same  class;  that  is,  under  similar  conditions  as  regards  work  or  rest. 

"For  several  years  an  effort  has  been  made  to  collect  statistical  and  experimental  data 
with  a  view  to  revising  dietary  standards.  The  amount  of  data  at  present  (1906)  available 
is  very  large,  and  the  work  of  systematizing  it  is  well  under  way.  It  seems  probable  that 
the  revised  dietary  standards  will  differ  somewhat  from  the  standards  pubUshed  in  this  and 
earUer  publications  of  this  Department. 
142 


37 

MAKING  HOME  STUDIES  OF  DIETARIES. 

Any  housekeeper  who  wishes  to  know  how  the  nutritive  value  of  the 
food  she  provides  for  her  family  corresponds  with  the  dietary  stand- 
ards can  easily  make  a  simple  dietary  study  in  her  homo,  and  ])y  so 
doing  can  perhaps  not  onh'  provide  meals  that  are  more  in  accordance 
with  the  needs  of  her  family,  but  frequently  also  save  money  by  sub- 
stituting less  expensive  but  equally  nutritious  and  attractive  food 
materials  for  some  of  those  usually  served. 

The  simplest  way  to  make  such  a  study  is  to  weigh  all  different 
kinds  of  food  materials  in  the  house  at  a  given  time,  sa}^  after  supper, 
recording  the  weights  in  a  convenient  book.  All  the  food  purchased 
during  the  days  during  wliich  the  diet  is  being  studied  is  weighed  and 
recorded,  and  at  the  close  of  the  study,  which  may  be  conveniently  of 
seven  or  ten  daj^s'  duration,  all  food-  materials  remaining  on  hand  are 
weighed  as  before.  From  the  quantities  of  the  different  kinds  of  food 
on  hand  at  the  beginning  and  purchased  during  the  period  are  sub- 
tracted the  quantities  left  on  hand  at  the  close  of  the  study.  The  dif- 
ference represents  the  amounts  used.  The  quantity  of  nutrients  in 
the  different  materials  is  calculated  from  the  figures  for  percentage 
composition  given  in  Table  I,  or  in  other  more  comprehensive  tables®. 
In  order  to  express  the  quantities  of  nutrients  in  values  per  man  per 
day,  the  number  of  meals  taken  by  different  members  of  the  family 
are  multiplied  by  the  factors  given  on  page  33,  pointing  off  one  deci- 
mal place.  The  result  gives  the  equivalent  number  of  meals  for  a 
man.  The  equivalent  number  of  meals  taken  divided  by  3  gives  the 
equivalent  number  of  days  for  one  man.  The  total  nutrients  for  the 
whole  period,  divided  by  this  latter  quantity,  gives  the  nutrients  per 
man  per  day.  From  these  latter  figures  the  fuel  value  of  the  diet  can 
be  computed  by  means  of  the  factors  given  on  page  33.  In  a  similar 
way  the  value  of  any  menu  for  one  day  or  one  meal  may  be  calculated. 
It  is  to  be  remembered  that  in  a  short  period,  such  as  a  day  or  two 
days,  the  diet  may  fluctuate  according  to  the  materials  used  so  as  to 
give  more  of  one  kind  of  nutrients  and  less  of  another,  or  more  or  less 
total  nutrients  than  the  average  diet,  while  in  periods  of  a  week  or  ten 
days  the  diet  is  more  likely  to  approach  an  average. 

ADAPTING  FOOD  TO  THE  NEEDS  OF  THE  BODY. 

All  persons  are  alike  in  that  they  must  have  protein  for  the  building 
and  repair  of  the  bodily  machine  and  fuel  ingredients  for  warmth  and 
work,  but  individuals  differ  in  the  amounts  and  proportions  they 
require,  and  even  among  those  in  good  health  there  are  many  who  are 
obliged  to  avoid  certain  kinds  of  food,  while  invalids  and  people  with 
weak  digestion  must  often  have  special  di(!t. 

•See  especially  U.  S.  Dcpt.  Apr.,  (Wkc.  of  Experiment  Stations  Bill.  2K,  rciviwd. 
M8 


38 

For  people  in  good  health  and  with  good  digestion  there  are  two 
important  rules  to  be  observed  in  the  regulation  of  the  diet.  The  first 
is  to  choose  the  things  which  "agree"  with  them,  and  to  avoid  those 
which  they  can  not  digest  and  assimilate  without  harm.  The  second  is 
to  use  such  kinds  and  amounts  of  food  as  will  supply  all  the  nutrients 
the  body  needs  and  at  the  same  time  avoid  burdening  it  with  superflu- 
ous material  to  be  disposed  of  at  the  cost  of  health  and  strength. 

For  guidance  in  this  selection,  nature  provides  us  with  instinct, 
taste,  and  experience.  Physiological  chemistry  adds  to  these  the 
knowledge — still  new  and  far  from  adequate — of  the  composition  of 
food  and  the  laws  of  nutrition.  In  our  actual  practice  of  eating  we 
are  apt  to  be  influenced  too  much  by  taste — that  is,  by  the  dictates  of 
the  palate;  we  are  prone  to  let  natural  instinct  be  overruled  by  acquired 
appetite,  and  we  neglect  the  teachings  of  experience.  We  need  to 
observe  our  diet  and  its  effects  more  carefully  and  to  regulate  appetite 
by  reason.  In  doing  this  we  may  be  greatly  aided  by  the  knowledge 
of  what  our  food  contains  and  how  it  serves  its  purpose  in  nutrition. 

Though  there  may  be  differences  among  abnormal  persons,  for  the 
great  majority  of  people  in  good  health  the  ordinary  food  materials — 
meats,fish,eggs,milk,butter,cheese, sugar,  flour,  meal,and  potatoes  and 
other  vegetables — make  a  fitting  diet,  and  the  main  question  is  to  use 
them  in  the  kinds  and  proportions  fitted  to  the  actual  needs  of  the  body. 

When  more  food  is  eaten  than  is  needed,  or  when  articles  difficult 
of  digestion  are  taken,  the  digestive  organs  are  overtaxed,  if  not  posi- 
tively injured,  and  much  energy  is  thus  wasted  which  might  have  been 
turned  to  better  account.  The  evils  of  overeating  may  not  be  felt  at 
once,  but  sooner  or  later  they  are  sure  to  appear — perhaps  in  an  exces- 
sive amount  of  fatty  tissue,  perhaps  in  general  debility,  perhaps  in 
actual  disease.  The  injurious  effects  of  food  which  does  not  "agree" 
with  a  person  have  already  been  pointed  out. 

ADVANTAGES  OF  SEVERAL  MEALS  A  DAY. 

The  theory  is  advanced  from  time  to  time  that  one  or  two  meals  a 
day  are  preferable  to  the  three  commonly  served  in  this  country.  If 
the  same  amount  of  food  is  to  be  eaten  it  is  hard  to  see  the  advantage 
of  two  very  hearty  meals  over  three  ordinary  ones.  The  best  physi- 
ological evidence  implies  that  moderate  quantities  of  food  taken  at 
moderate  intervals  are  more  easily  and  completely  digested  by  ordi- 
nary people  than  larger  quantities  taken  at  long  intervals.  If  the 
food  ordinarily  taken  is  considered  excessive  and  the  aim  is  simply  to 
reduce  the  amount,  it  would  seem  more  rational  to  make  all  the  meals 
lighter  than  to  leave  out  one.  The  very  fact  that  the  custom  of  eating 
a  number  of  meals  a  day  has  so  long  been  almost  universal  indicates 
that  it  must  have  some  advantages  which  instinct,  based  upon  experi- 
ence, approves  and  justifies. 


39  •^ 

PECTJNIAKY  ECONOMY  OF  FOOD. 

Although  the  cost  of  food  is  the  principal  item  in  the  living  expenses 
of  a  large  majority  of  the  people,  and  although  the  physical  welfare  of 
all  is  so  intimately  connected  with  and  dependent  upon  diet,  very  few 
of  even  the  most  intelligent  have  any  clear  ideas  regarding  the  actual 
nutriment  in  the  different  food  materials  they  use.  In  too  many  cases 
even  those  who  wish  and  try  to  economize  know  very  little  as  to  the 
combinations  which  are  best  fitted  for  their  nourishment  and  have  still 
less  information  as  to  the  relation  between  the  real  nutritive  value  of 
different  foods  and  their  cost. 

The  question  here  to  be  considered  is  this:  Of  the  different  food 
materials  which  are  palatable,  nutritious,  and  otherwise  suited  for 
nourishment,  what  ones  are  pecuniarily  the  most  economical ;  in  other 
words,  what  ones  furnish  the  largest  amounts  of  available  nutrients  at 
the  lowest  cost  ?  In  answering  this  question  it  is  necessary  to  take 
into  account  not  only  the  prices  per  pound,  quart,  or  bushel  of  the  dif- 
ferent materials,  but  also  the  kinds  and  amounts  of  the  actual  nutri- 
ents they  contain  and  their  fitness  to  meet  the  demands  of  the  body  for 
nourishment.  The  cheapest  food  is  that  which  supplies  the  most  nutri- 
ment for  the  least  money.  The  most  economical  food  is  that  which  is 
cheapest  and  at  the  same  time  best  adapted  to  the  needs  of  the  user. 

There  are  various  ways  of  comparing  food  materials  with  respect  to 
the  relative  cheapness  or  deamess  of  their  nutritive  ingredients.  For 
instance,  from  the  proportions  of  available  nutrients  and  energy  in 
different  food  materials  given  in  Table  III  we  may  calculate  the  cost 
of  the  different  nutrients  per  pound  and  of  energy  per  1,000  calories 
in  any  given  material  for  which  the  price  per  pound  is  known.  Thus, 
for  the  different  food  materials  given  in  Table  V  (p.  40),  when  the 
price  of  any  material  is  that  given  in  the  first  column,  the  cost  of  pro- 
tein and  energy  will  l^e  as  given  in  the  second  and  third  columns. 
These  figures  show  the  relative  economy  of  the  various  foods  as  sources 
of  protein  and  sources  of  energy.  Of  course  the  amount  of  energy 
that  would  be  obtained  in  a  quantity  of  any  given  material  sufficient 
to  furnish  a  pound  of  protein  would  vary  with  the  amounts  of  fats  and 
carbohydrates  accompanying  the  protein;  and  on  the  other  hand,  the 
quantities  of  the  different  materials  that  would  furnish  1,000  calories 
of  energ}'  would  contain  different  amounts  of  protein.  The  figures 
for  cost  of  protein  leave  the  carbohydrates  and  fats  out  of  account,  and 
tho.se  for  energy  take  no  account  of  the  protein.  Hence  the  figures 
for  either  protein  or  energy  alone  give  a  very  one-sided  view  of  the  rela- 
tion between  nutritive  value  and  money  cost. 

A  better  way  of  estimating  the  relative  pecuniary  economy  of  differ- 
ent food  materials  is  found  in  a  comparison  of  the  (|uantities  of  both 
nutrients  and  energy  wliich  can  be  obtained  for  a  given  sum,  say  10 

143 


40 

cents,  at  current  prices.     This  also  is  illustrated  in  Table  V,  which 
follows : 

Table  V. — Comparative  cost  of  digestible  nutrients  and  energy  in  different  food  materials  at 

average  prices. 

[It  is  estimated  that  a  man  at  light  to  moderate  muscular  work  requires  about  0.23  pound  of  protein 
and  3,050  calories  of  energy  per  day.] 


Kind  of  food  material. 


Beef,  sirloin 

Do 

Do 

Beef,  round 

Do 

Do 

Beef,  shoulder  clod 

Do 

Beef,  stew  meat 

Beef,  dried,  chipped 

Mutton  chops,  loin 

Mutton,  leg 

Do 

Roast  pork,  loin 

Pork,  smoked  ham 

Do 

Pork,  fat  salt 

Codfish,  dressed,  fresh 

Halibut,  fresh 

Cod,  salt 

Mackerel,  salt,  dressed 

Salmon,  canned 

Oysters,    solids,    50   cents    per 

quart 

Oysters,    solids,    35   cents   per 

quart 

Lobster,  canned 

Butter 

Do 

Do 

Eggs,  36  cents  per  dozen 

Eggs,  24  cents  per  dozen 

Eggs,  12  cents  per  dozen 

Cheese 

Milk,  7  cents  per  quart 

Milk,  6  cents  per  quart 

Wheat  flour 

Do 

Corn  meal,  granular 

Wheat  breakfast  food 

Oat  breakfast  food 

Oatmeal 

Rice 

Wheat  bread 

Do 

Do 

Rye  bread 

Beans,  white,  dried 

Cabbage 

Celery 

Corn,  canned 

Potatoes,  90  cents  per  bushel . . 
Potatoes,  60  cents  per  bushel . . 
Potatoes,  45  cents  per  bushel . . 

Turnips 

Apples 

Bananas 

Oranges 

Strawberries 

Sugar 


Price 

per 

pound. 


Cents. 
25 
20 
15 
16 
14 
12 
12 
9 
5 
25 
16 
20 
16 
12 
22 
18 
12 
10 
18 
7 
10 
12 


Cost  of 
1  pound 
pro- 
tein, a 


Dollars. 

1.60 

1.28 

.96 

.87 

.76 

.65 

.75 

.57 

.35 

.98 

1.22 

1^37 

1.10 

.92 

1.60 

1.30 

6.67 

.93 

1.22 

.45 

.74 

.57 

4.30 

3.10 

1.02 

20.00 

25.00 

30.00 

2.09 

1.39 

.70 

.64 

1.09 

.94 

.31 

.26 

.32 

.73 

.53 

.29 

1.18 

.77 

.64 

.51 

.65 

.29 

2.08 

6.65 

4.21 

1.00 

.67 

.50 

1.33 

5.00 

10.00 

12.00 

8.75 


Cost  of 

1,000 

calories 

energy 

(a) 


Cents. 
25 
20 
15 
18 
16 
13 
17 
13 

7 

32 
11 
22 
18 
10 
13 
11 

3 
46 
38 
22 

9 
13 

111 


Amounts  for  10  cents. 


Total 
weight 
of  food 
mate- 
rial. 


Pounds 

0.40 
.50 
.67 
.63 
.71 
.83 
.83 

1.11 

2 
.40 
.63 
.50 
.63 
.83 
.45 
.56 
.83 

1 
.56 

1.43 

1 
.83 

.40 

.56 

.56 

.50 

.40 

.33 

.42 

.63 

1.25 

.63 

2.85 

3.33 

3.33 

4 

4 

1.33 
1.33 
2.50 
1.25 
1.67 
2 

2.50 
2 
2 
4 
2 
1 

6.67 
10 

13.33 
10 

6.67 
.1.43 
1.67 
1.43 
1.67 


Pro- 
tein. 


Pound. 
0.06 
.08 
.10 
.11 
.13 
.15 
.13 
.18 
.29 
.10 
.08 
.07 
.09 
.11 
.06 
.08 
.02 
.11 
.08 
.22 
.13 
.18 


Fat. 


Pound. 
0.06 
.08 
.11 
.08 
.09 
.10 
.08 
.10 
.23 
.03 
.17 
.07 
.09 
.19 
.14 
.18 


.02 
.01 
.20 
.10 


.02 

.03 

.01 

.10 

.01 

.01 

.40 

.32 

.27 

.04 
.06 
.11 
.20 
.11 
.13 
.03 
.04 
.07 
.02 
.09 
.16 


.02 
.02 
.03 
.01 
.03 
.01 


.01 
.01 
.01 
.01 
.01 
.02 
.01 


Carbohy- 
drates. 


Pounds. 


.01 
.02 


.02 

.14 

.17 

2.45 

2.94 

2.96 


1.66 

.97 

.87 

1.04 

1.30 

1.04 

1.16 

.18 

.05 

.18 

.93 

1.40 

1.87 

.54 

.65 

.18 

.13 

.09 

1.67 


a  The  cost  of  1  pound  of  protein  means  the  cost  of  enough  of  the  given  material  to  furnish  1  pound  of 
protein,  without  regard  to  the  amounts  of  the  other  nutrients  present.  Likewise  the  cost  of  energy 
means  the  cost  of  enough  material  to  furnish  1,000  calories,  without  reference  to  the  kinds  and  propor- 
tions of  nutrients  in  which  the  energy  is  supplied.  These  estimates  of  the  cost  of  protein  and  energy 
are  thus  mcorrect  in  that  neither  gives  credit  for  the  value  of  the  other. 

142 


41 


The  fourth  cokmin  in  Table  Y  shows  the  total  weight  of  each  food 
material  and  the  last  four  columns  the  amounts  of  different  nutrients 
and  of  energy  that  can  be  obtained  for  10  cents  when  the  })rice  per 
poimd  is  that  given  in  the  fiist  column.  Chart  2  illustrates  graphically 
the  facts  brought  out  in  this  part  of  the  table. 

Chabt  2.— pecuniary  ECONOMY'  OF  FOOD. 

Anwunts  of  actually  nutritive  ingredients  obtained  in  differefitfood  materials  for  10  cents. 
[Amounts  of  nutrients  in  pounds;  fuel  value  in  calories.] 
J^tein.  Rvts  Carhoki/dratu         Fuel  Value. 


42 

Of  course,  the  market  prices  of  the  different  food  materials  would 
vary  in  different  localities  and  at  different  times,  but  the  prices  here 
used  are  averages  of  such  as  are  actually  found  in  different  parts  of 
the  United  States  in  different  years  and  seasons,  and  serve  for  coni- 
parison. 

It  should  be  borne  in  mind  that  the  figures  here  given  represent 
only  the  cost  of  the  materials  as  purchased  in  the  market.  In  com- 
paring the  relative  economy  of  the  different  food  materials  no  account 
is  taken  of  the  cost  of  cooking  or  of  the  convenience  of  preparation  for 
the  table,  which  are  sometimes  even  more  important  from  the  stand- 
point of  actual  economy  than  the  market  prices. 

The  figures  of  Table  V  show,  for  instance,  that  10  cents  spent  for 
beef  sirloin  at  20  cents  a  pound  buys  0.5  pound  of  meat,  which  con- 
tains 0.08  pound  of  protein,  0.08  pound  of  fat,  and  515  calories  of  energy, 
actually  available  to  the  body,  while  the  same  amount  spent  for  oysters 
at  35  cents  a  quart  would  buy  a  little  over  half  a  pound  of  oysters,  con- 
taining 0.03  pound  of  protein,  0.01  pound  of  fat,  0.02  pound  of  carbo- 
hydrates, and  125  calories  of  energy;  or  if  spent  for  cabbage,  at  2| 
cents  a  pound,  it  would  buy  4  pounds,  containing  0.05  pound  of  pro- 
tein, 0.01  pound  of  fat,  0.18  pound  of  carbohydrates,  and  460  calories 
of  energy,  while  of  wheat  flour  at  3  cents  a  pound  it  would  buy  3  J 
pounds,  containing  0.32  pound  of  protein,  0.03  pound  of  fat,  2.45 
pounds  of  carbohydrates,  and  5,410  calories  of  energy.  Comparing 
the  various  materials  in  this  way,  it  becomes  clear  that  the  fresh  vege- 
tables are  the  dearest  sources  of  protein,  meats  and  fish  somewhat 
cheaper,  and  the  cereals  cheapest  of  all ;  and  that  oysters  and  lobsters 
are  the  costliest  sources  of  energy,  followed  by  some  of  the  green  vege- 
tables and  fruits,  then  the  majority  of  the  meats,  next  potatoes,  and 
cheapest  of  all,  the  cereals. 

It  is  quite  evident  that  the  market  price  of  food  materials  is  not 
regulated  by  their  actual  value  for  nutriment.  For  instance,  an  ounce 
of  protein  or  fat  from  the  tenderloin  of  beef  is  no  more  nutritious  than 
that  from  a  round  or  shoulder,  but  it  costs  considerably  more.  The 
agreeableness  of  food  to  the  palate  or  to  the  buyer's  fancy  has  much  to 
do  in  deciding  current  demand  and  consequent  selling  price.  It  may 
be  said,  however,  that  animal  foods  have  some  advantage  over  vege- 
table foods.  Animal  foods,  such  as  meats,  fish,  milk,  and  the  like, 
gratify  the  palate  as  many  vegetable  foods  do  not.  Furthermore, 
what  is  of  still  greater  weight  in  regulating  the  food  habits  of  communi- 
ties by  whose  demand  the  prices  are  determined,  they  satisfy  an  actual 
need  by  supplying  protein  and  fats  in  which  the  vegetable  foods,  except 
cereal  grains  and  leguminous  seeds,  are  largely  lacking.  Moreover, 
as  has  previously  been  explained,  the  animal  foods  are  in  general  more 
easily  and  completely  digested  than  are  the  vegetable,  especially  as 
regards  protein.     Thus  there  is  doubtless  good  ground  for  paying 

142 


43 

somewhat  more  for  the  same  total  quantity  of  nutritive  material  in 
the  animal  food. 

One  point  to  be  especially  noted  here  is  the  difference  in  the  cost  of 
nutrients  in  foods  already  prepared  for  use  and  in  the  same  materials 
not  so  prepared.  For  instance,  wheat  made  into  ordinary  prepared 
breakfast  cereal  might  contain  no  more  available  protein  or  energy 
than  the  same  wheat  made  into  white  or  graham  flour,  but  the  break- 
fast cereals  cost  more  than  the  flour  per  pound.  At  the  same  time, 
the  breakfast  foods  afford  a  pleasing  variety  in  the  diet,  and  often 
require  little  or  no  cooking  and  are  therefore  very  convenient;  while 
the  fioiu-  must  be  made  into  bread  or  other  food  at  more  expense  of 
labor,  fuel,  etc.  If  the  breakfast  cereal  does  not  cost  much  more  than 
the  flour  the  difference  may  be  offset  by  the  convenience  of  prepara- 
tion for  the  table,  the  palatabihty,  and  the  pleasing  variety  it  gives. 

Many  of  the  breakfast  foods  are  advertised  as  having  an  especially 
high  nutritive  value.  If  the  statements  often  made  m  advertising 
these  could  be  beUeved  they  would  have  some  nutritive  property  not 
found  in  flours  and  meals  groimd  from  the  same  grains.  For  these 
claims  there  is  no  ground.  The  breakfast  foods  made  from  wheat, 
com,  oats,  and  other  cereals  contain  no  nutritive  material  other  than 
that  which  is  in  the  original  grain,  and  which  is  also  found  in  the  ordi- 
nary flours  and  meals  made  from  the  same  grains;  and  when  the  two 
kinds  of  food  are  equally  well  cooked  there  is  no  experimental  evidence 
to  show  any  difference  in  the  thoroughness  of  digestibility.  The  retail 
prices  of  the  breakfast  foods  are  from  two  to  five  times  as  large  as 
those  of  the  ordinary  products,  like  flour  and  meal.  The  advertise- 
ments, which  often  claim  nutritive  values  that  are  fictitious,  do  not 
give  any  suggestion  of  the  high  price  of  the  nutrients  in  the  prepared 
foods  as  compared  with  that  of  the  same  amounts  in  the  ordinary 
products,  nor  do  purchasers  generally  reaUze  how  expensive  these  pre- 
pared foods  are. 

ERRORS  IN  FOOD  ECONOMY. 

Scientific  research,  interpreting  the  observationa  of  practical  life, 
indicates  that  a  fourfold  mistake  in  food  economy  is  very  commonly 
made.  First,  the  costlier  kinds  of  food  are  used  when  the  less  expen- 
sive are  just  as  nutritious  and  can  bo  made  nearly  or  quite  as  palatal)lo. 
Secondly,  the  diet  is  apt  to  be  one-sided,  in  that  foods  are  used  which 
furnish  relatively  too  much  of  the  fuel  ingredients  and  too  little  of  the. 
flesh-forming  materials.  Thirdly,  excessive  quantities  of  food  are 
used;  part  of  the  excess  is  eat<;n  and  often  to  the  detriment  of  health; 
part  is  thrown  away  in  the  table  and  kitchen  wastes.  Finally,  serious 
errors  in  cooking  are  committed. 

For  the  well-to-do  the  worst  injury  is  that  to  health;  but  people  of 
small  incomes  suffer  the  additional  disadvantage  of  the  injury  to  purse. 


44 

Indeed,  to  one  who  looks  into  the  matter  it  is  surprising  to  see  how 
much  people  of  limited  incomes  lose  in  these  ways.  It  is  the  poor 
man's  money  that  is  most  injudiciously  spent  in  the  market  and  the 
poor  man's  food  that  is  most  badly  cooked  at  home. 

NEEDIZESS  USE  OF  EXPENSIVE  FOODS. 

A  common  mistake  in  pui'chasing  food  is  in  buying  the  more  expen- 
sive kinds  when  cheaper  ones  would  serve  the  purpose  just  as  well. 
This  is  often  done  under  the  impression  that  there  is  some  pecuhar 
virtue  in  the  costlier  materials  and  that  economy  in  the  diet  is  detri- 
mental to  dignity  and  welfare.  Unfortunately  it  is  too  often  the  case 
that  those  who  are  most  extravagant  in  this  respect  are  the  ones  who 
can  least  afford  it.  On  the  other  hand,  there  is  frequently  a  desire 
to  economize,  but  a  lack  of  knowledge  of  the  best  method  of  doing  so. 
Many  a  housekeeper  who  sincerely  tries  to  do  the  best  for  those  to  be 
provided  for,  but  whose  every  cent  must  tell,  buys  eggs  at  25  cents  a 
dozen,  or  sirloin  steak  at  20  cents  a  pound,  when,  for  the  same  amoimt 
of  money,  it  would  be  possible  to  get  twice  as  much  nourishment  from 
a  cheaper  cut  of  meat,  which,  with  a  little  skill  in  preparation  and 
cooking,  could  be  made  into  a  tasty  dish  such  as  persons  in  far  easier 
circumstances  would  not  hesitate  to  set  upon  their  tables. 

The  difficulty  is  the  ignorance  of  the  simple  principles  of  nutrition. 
That  ignorance  results  in  a  great  waste  of  money.  The  maxim  "that 
the  best  is  the  cheapest,"  as  popularly  understood  to  apply  to  the 
higher-priced  materials,  is  not  true  of  food.  The  larger  part  of  the 
price  of  the  costlier  foods  is  paid  for  appearance,  flavor,  or  rarity. 
While  the  dearer  articles  are  often  more  pleasing  to  the  palate,  and 
are  sometimes  more  easily  cooked  or  possess  a  finer  flavor,  they  are 
no  more  digestible  nor  nutritious  than  the  cheaper  ones.  People  who 
can  afford  them  may  be  justified  in  buying  them,  but  for  persons  in 
good  health  and  with  limited  means  they  are  not  economical,  and  often 
increase  the  cost  of  food  out  of  all  proportion  to  nutrients  furnished. 

In  the  course  of  some  dietary  studies  made  in  one  of  the  poorer  dis- 
tricts of  Chicago  it  was  found  that  a  woman,  whose  husband  was  out 
of  work  and  whose  family  was  living  on  a  few  cents  a  day,  bought 
lettuce,  an  article  so  innutritions  that,  at  least  when  out  of  season 
and  high  in  price,  it  is  a  luxury  even  for  the  rich,  while  she  had  to  do 
without  nutritious  food.  No  one  can  object  to  the  use  of  lettuce,  or 
any  other  wholesome  food,  when  the  purse  allows,  but  it  is  pitifully 
bad  economy  in  such  cases  to  buy  foods  which  simply  please  the  palate 
while  the  body  goes  without  proper  nourishment. 

The  plain,  substantial,  standard  food  materials,  like  the  cheaper 
cuts  of  meat  and  fish,  milk,  flour,  com  meal,  oatmeal,  beans,  and  pota- 
toes, are  as  digestible  and  nutritious  and  as  well  fitted  for  the  nourish- 
ment of  people  in  good  health  as  are  any  of  the  costlier  materials. 

We  endeavor  to  make  our  diet  suit  our  palate  by  paying  high  prices 
in  the  market  rather  than  by  skillful  cooking  and  tasteful  serving 


45 

at  home.  The  remedy  for  this  evil  will  be  found  in  an  understanding 
of  the  elementary  facts  regarding  food  and  nutrition,  in  a  better 
knowledge  of  cooking  and  serving  food,  and  in  the  acceptance  of  the 
doctrine  that  economy  is  not  only  respectable  but  honorable. 

The  soup  kitchens  which  have  been  established  in  many  cities, 
where  meals  planned  according  to  accepted  dietary  standards  are  sold 
at  very  low  and  yet  profitable  rates,  should  furnish  their  patrons  with 
object  lessons  on  the  food-purchasing  power  of  money. 

DANGER  OF  A  ONE-SIDED  DIET. 

Unless  care  is  exercised  in  selecting  food  a  diet  may  result  wliich  is 
one-sided  or  badly  balanced — that  is,  one  in  wliich  either  protein  or 
fuel  ingredients  are  provided  in  excess.  If  a  person  consumes  large 
amounts  of  meat  and  little  vegetable  food,  the  diet  will  be  too  rich  in 
protein  and  may  be  harmful.  On  the  other  hand,  if  pastry,  butter, 
and  such  foods  are  eaten  in  preference  to  a  more  varied  diet,  the  food 
will  furnish  too  much  energy  and  too  little  building  material. 

Extreme  illustrations  of  such  a  one-sided  diet  are  found  in  the  food 
of  those  persons  who  live  largely  on  bread  and  tea,  or  others  who  live 
on  com  meal,  fat  pork,  and  molasses.  The  "hog  and  hominy"  diet 
supplies  liberal  quantities  of  energy,  but  is  very  deficient  in  protein, 
as  illustrated  by  the  diet  of  negroes  in  the  "black  belt,"  with  62  grams 
of  protein  and  3,270  calories  of  energy  per  man  per  day. 

In  this  connection  it  should  be  said  that  most  of  our  dietary  stand- 
ards have  been  deduced  from  food  investigations  conducted  with  per- 
sons living  in  temperate  climates.  It  is  not  improbable  that  those 
living  in  arctic  regions  and  in  the  Tropics  require  nutrients  in  different 
proportions.  It  is  a  matter  of  common  observation  that  in  arctic 
regions  much  larger  amounts  of  energy-yielding  material,  principally 
fat,  are  consumed  than  in  warmer  climates.  Less  definite  informa- 
tion is  available  regarding  food  requirements  in  the  Tropics;  but  it 
seems  probable  that  when  proper  dietary  conditions  are  followed  some- 
what less  food  is  consumed  than  in  temperate  regions,  and  that  the 
nutrients  are  in  somewhat  difi"erent  proportion.  It  is  certain  that  a 
diet  which  would  be  entirely  satisfactory  in  frigid  regions  would  be 
one-sided  in  the  Tropics,  and  vice  versa.  This  subject  is  one  which 
needs  further  investigation  before  definite  conclusions  can  be  drawn 
regarding  the  foods  best  fitted  for  extremes  of  heat  or  cold. 

"WASTE  OF  FOOD. 

The  use  of  excessive  quantities  of  food,  which  is  a  common  dietary 
error  in  this  country,  among  not  only  the  well  to  do  but  also  those  in 
moderate  circumstances,  entails  a  waste  of  food  in  at  least  three  ways: 

First.  More  food  is  eaten  than  can  be  properly  utilized  by  the  l)ody. 
Tliis  is  not  universally  true,  for  there  are  some  people  who  do  not  cat 
enough  for  healthful  nourishment.  But  the  eating  liabits  of  largo 
numbers  are  vicious,  resulting  not  only  in  a  loss  of  food  material  but 
ID  an  increase  in  the  labor  of  digestion,  to  say  nothing  of  the  injurious 

142 


46 

effects  which  overeating  may  have  upon  the  bodily  organs  and  func- 
tions and  upon  health  in  general.  Probably  the  worst  sufferers  from 
this  evil  are  well-to-do  people  of  sedentary  occupations — brain  work- 
ers as  distinguished  from  hand  workers. 

Second.  More  food  is  served  than  can  be  eaten,  and  the  excess  is 
thrown  away  as  table  waste.  Indeed,  in  many  families  in  this  country 
it  is  a  matter  of  pride  to  furnish  more  food  than  is  needed,  a  feeling 
which  appears  quite  unreasonable  to  frugal  Europeans,  even  those  in 
equally  comfortable  circumstances. 

Third.  The  third  form  is  that  which  occurs  in  the  preparation  of 
food  materials  for  consumption.  Thus,  in  removing  the  inedible  mate- 
rial, as  skin,  seeds,  etc.,  from  fruits  and  vegetables,  more  or  less  of 
the  edible  portion  is  removed  also,  depending  upon  the  care  with 
which  the  work  is  done.  The  greatest  loss  from  a  pecuniary  stand- 
point, however,  is  in  the  waste  of  animal  foods  in  which  the  nutrients  are 
in  their  costliest  forms.  The  ' '  trimmings  "  of  meat  which  are  left  with 
the  butcher  or  removed  in  the  kitchen  frequently  contain  one-eighth  of 
the  nutritive  ingredients  of  the  material  paid  for.  Part  of  such  waste 
is  inevitable,  but  much  of  the  valuable  nutrients  might  be  saved  if  the 
materials  were  used  for  making  soup.  The  more  economical  cuts  of 
meats  are  those  in  which  there  is  less  waste  of  this, kind;  in  such  cuts  of 
meat  as  loin  of  beef,  rib  chops  of  lamb,  and  similar  cuts,  one-fifth  the 
cost  goes  to  pay  for  bone.  Such  cuts,  therefore,  should  be  avoided 
by  those  who  wish  to  get  the  most  actual  nutriment  for  their  money. 

Just  where  and  among  what  classes  of  people  the  waste  of  food  is 
greatest  it  is  not  possible  to  say,  but  there  is  certainly  a  great  deal 
more  of  it  in  this  country  than  in  Europe.  The  worst  sufferers  from 
it  are  doubtless  the  poor,  but  the  large  body  of  people  of  moderate 
means,  the  intelligent,  and  fairly  well-to-do  wage- workers  are  guilty  of 
errors  in  this  regard.  The  common  remark  that  ''the  average  Amer- 
ican family  wastes  as  much  food  as  a  French  family  would  live  upon" 
is  greatly  exaggerated,  but  statistics  show  that  there  is  considerable 
truth  in  it.  In  dietary  studies  conducted  at  a  students'  club  in  an 
Eastern  college  it  was  found  that  10  to  14  per  cent  of  the  nutritive 
materials  purchased  were  thrown  away  as  kitchen  or  table  waste,  and 
yet  the  club  members  were  trying  to  live  as  economically  as  was  con- 
sistent with  comfort.  In  private  families  the  waste  has  been  found  to 
range  from  practically  none  to  as  high  as  8  or  10  per  cent,  while  in 
boarding  houses,  even  where  economy  was  sought,  it  has  reached  10, 
and  in  individual  instances  20  per  cent;  and  in  some  public  institu- 
tions where  large  numbers  were  fed  it  has  been  as  high  as  25  per  cent 

and  even  higher. 

EKBORS  IN  COOKING. 

It  is  commonly  remarked  by  those  who  study  the  conditions  of  liv- 
ing of  people  of  limited  means  in  different  parts  of  the  country  that 

142 


47 

for  suhstautial  improvement  of  their  household  economics  two  things 
are  needed.  They  must  be  informed  as  to  the  high  nutritive  value  of 
the  cheaper  foods  as  compared  \vith  the  costlier  kinds,  and  the  meth- 
ods of  cooking  must  be  improved.  A  great  deal  of  fuel  is  wasted  in  the 
preparation  of  food,  and  even  then  a  great  deal  of  the  food  is  badly 
cooked.  To  replace  dear  food  badly  cooked  by  cheaper  food  well 
cooked  is  important  for  both  health  and  purse.  To  make  the  table 
more  attractive  will  be  an  efficient  means  for  making  the  home  Ufe 
more  enjoyable. 

SUMMARY. 

Food  has  been  briefly  defined  as  ''that  which  taken  into  the  body, 
either  builds  tissue  or  yields  energy."  In  its  btiilding  function  pro- 
tein is  the  most  important  iiigredient  of  food,  as  it  is  the  basis  of  mus- 
cle, bone,  and  almost  all  the  tissues  and  fluids  of  the  body.  Mineral 
matters  are  also  needed  in  the  body  structure,  though  in  smaller  quan- 
tities. Protein,  fats,  and  carbohydrates  may  any  of  them  be  burned 
in  the  body  to  produce  heat  or  muscular  energy,  but  for  protein  this 
is  a  less  important  and  probably  less  usual  function.  The  fats  and 
carbohydrates,  by  being  themselves  used  as  fuel,  leave  the  protein  for 
its  indispensable  work  of  tissue  forming. 

Not  only  the  amounts  of  nutritive  ingredients  which  a  food  contains, 
but  also  the  proportions  which  can  be  digested  and  utilized  by  the 
body,  determine  the  real  nutritive  value  of  a  food  material.  As  a 
general  rule,  carbohydrates  are  more  completely  digested  and  hence 
more  fully  available  for  use  in  the  body  than  protein  and  fats,  and 
protein  of  animal  foods,  as  meat,  fish,  milk,  and  eggs,  is  more  digest- 
ible than  that  of  vegetable  foods.  Fats  are  probablly  less  digestible 
than  most  forms  of  protein  and  carbohydrates. 

In  ordinary  mixed  diet  the  chief  sources  of  protein  are  meat,  fish, 
and  milk  among  animal  foods,  and  the  cereals  and  legumes  among 
vegetable  foods.  Beans,  peas,  and  oatmeal  are  rich  in  protein  and 
hence  especially  valuable  food.  About  nine-ttmths  of  the  fat  in  the 
ordinary  diet  is  obtained  from  the  animal  foods,  while  the  vegetable 
foods  furnish  approximately  nine-tenths  of  the  carbohydrates. 

Othf^r  things  being  equal,  foods  furnishing  nutrients  wliich  can  be 
most  easily  and  completely  utilized  by  the  body  are  the  most  desirable, 
since  they  will  not  bring  unnecessary  exertion  to  the  various  organs. 
Many  kinds  of  food  which  in  their  natural  state  hold  the  most  valuable 
nutrients  in  such  form  that  the  digestive  juices  can  not  easily  work 
upon  them  are  so  changed  by  the  heat  of  cooking  that  they  become 
easily  digf^stible.  Thus  the  importance  of  proper  cooking  can  hardly 
be  overesti fruited.  Things  whi(;h  please  the  palatt^  stinniiate  th(^  Mow 
of  the  dige.stive  juices;  for  this  rea.son  food  should  \hi  made  appetizing. 
An  attractive  diet  pleases  the  aesthetic  sense;  hence  reiinemcnt  in  food 


48 

habits  is  as  desirable  as  in  other  phases  of  our  daily  Ufe.  The  sense  of 
comfort  and  satisfaction  produced  by  even  the  appearance  of  food  well 
cooked  and  served  is  of  indisputable  value.  Fortunately  such  satis- 
faction is  within  the  reach  of  almost  all. 

Among  people  who  have  the  benefits  of  modern  comfort  and  culture 
the  palate  revolts  against  a  very  simple  and  unvaried  diet,  and  for  this 
reason  the  nutrients  are  usually  supplied  from  a  variety  of  articles — 
some  of  animal,  some  of  vegetable  origin.  With  a  varied  diet  it  is  also 
easier  to  secure  the  proper  proportions  of  protein  to  fats  and  carbohy- 
drates. 

As  the  habits  and  conditions  of  individuals  differ,  so,  too,  their 
needs  for  nourishment  differ,  and  their  food  should  be  adapted  to  their 
particular  requirements.  It  has  been  estimated  that  an  average  man 
at  moderately  active  labor,  like  a  carpenter  or  mason,  should  have 
about  115  grams  or  0.25  pound  of  available  protein  and  sufficient  fuel 
ingredients  in  addition  to  make  the  fuel  value  of  the  whole  diet  3,400 
calories,  while  a  man  at  sedentary  employment  would  be  well  nour- 
ished with  92  gramis  or  0.20  pound  of  available  protein  and  enough 
fats  and  carbohydrates  in  addition  to  yield  2,700  calories  of  energy. 
The  demands  are,  however,  variable,  increasing  or  decreasing  with 
increase  or  decrease  of  muscular  work,  or  as  other  needs  of  the  person 
change.  Each  person,  too,  should  learn  by  experience  what  kinds  of 
food  yield  him  nourishment  with  the  least  discomfort,  and  should 
avoid  those  which  do  not  "agree"  with  him. 

Too  much  food  is  as  bad  as  too  little  and  occasions  a  waste  of  energy 
and  strength  in  the  body  as  well  as  a  waste  of  nutritive  material. 
While  in  the  case  of  some  foods  as  purchased,  notably  meats,  some 
waste  is  unavoidable,  the  pecuniary  loss  can  be  diminished,  both  by 
buying  those  kinds  in  which  there  is  the  least  waste,  and  by  utilizing 
more  carefully  than  is  ordinarily  done  portions  of  what  is  usually 
classed  as  refuse.  Much  of  the  waste  may  be  avoided  by  careful  plan- 
ning so  as  to  provide  a  comfortable  and  appetizing  meal  in  sufficient 
amount,  but  without  excess.  If  strict  economy  is  necessary,  the  dearer 
cuts  of  meat  and  the  more  expensive  fruits  and  vegetables  should  be 
avoided.  With  reasonable  care  in  cooking  and  serving,  a  pleasing  and 
varied  diet  can  be  furnished  at  moderate  cost.  It  should  not  be  for- 
gotten that  the  real  cheapness  or  dearness  of  a  food  material  depends 
not  only  on  its  market  price,  but  also  on  the  cost  of  its  digestible 
nutrients.  It  should  always  be  remembered  that  "the  ideal  diet  is 
that  combination  of  foods  which,  while  imposing  the  least  burden  on 
the  body,  supplies  it  with  exactly  sufficient  material  to  meet  its 
wants,"  and  that  any  disregard  of  such  a  standard  must  inevitably  pre- 
vent the  best  development  of  our  powers. 


o 


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1910 


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